Shinpei Ajiro (網代 慎平, Ajiro Shinpei) is a 17-year-old boy who returned to his hometown of Hitogashima for the first time in two years to attend the funeral of his childhood friend, Ushio Kofune. Since he lost his parents at an early age and grew up in the Kofune family, he has been close to Ushio and Mio as if they were his family. He has a habit of trying to "look down" on his situation objectively.
Shinpei is a young man with medium long black hair and blue eyes. He usually wears a white shirt and blue shorts.
After two years away, Shinpei returns to Hitogashima to attend his childhood friend Ushio's funeral. On the boat, he dreams of she asking him to find her and protect Mio. Stepping on the island, Mio welcomes him and they head towards the funeral while chatting about various subjects. At the funeral, his friend Sou explains that Ushio saved a kid, Shiori Kobayakawa, from drowning, but drowned herself. That evening, Sou calls Shinpei and explains that the rumour about his father performing an autopsy on Ushio isn't real, but they did find strangler marks on Ushio's neck. However, as there was no one around suspicious at her death, they labelled it as incident.
The next day, Shinpei helps out at Kofune's dinner. A drunk man, Nakamura asks him if he found the woman with glasses he was looking for, but Shinpei thinks he confused him for someone else. The police officer, Tetsu comes and explains that the whole Kobayakawa family had vanished. Hearing that, Mio runs away and Shinpei follows her. After catching up to her, Mio explains that Shiori said she saw a girl looking like her about a week before the incident. An old hunter, Ginjiro Nezu, tells them that's a shadow and those afflicted by shadow sickness, see their shadow and then get killed by it. The shadow then acts as the killed person and kills the remaining family. It used to be quite common sickness before the war and those afflicted went to Hito shrine for cleansing. Mio then states she saw Ushio's shadow along with Ushio, three days before Ushio died. Shinpei then decide they go to the shrine to learn more about the shadows. However, the shrine is closed at the moment and Mio sees Shiori in the forest and they run after her. They are unable to find Shiori, but hear a gunshot and following the sound, they see the woman with glasses bleeding from a gunshot. Mio heads to get help and the woman tries to tell Shinpei something, but get shot in the head. Shinpei then sees Mio holding a gun and holding the Mio that was with him as hostage. The other Mio then shoots Mio and Shinpei. Shinpei then awakens back at the boat where he met the woman with the glasses.
Shinpei realizes his day is repeating and notices Mio's bike had a cut break wire. That night after preparing dinner, he goes out for a fresh air, thinking if someone tried to kill Mio. He ends up seeing Tetsu who sees Mio standing in front of the house. Mio then kills him with a kitchen knife and creates a shadow that transforms into Tetsu, making Shinpei realize she is a Shadow too. She takes Tetsu's gun and explains she wasn't able to kill Mio yet. However, Sou calls Shinpei, which reveals him and Mio kills him. She starts to explain why she can't make a copy of him, but Shinpei dies before he can hear the rest. Shinpei then finds himself travelling somehow and awakening on July 22nd as he steps on Hitogashima.
This time, Shinpei tries to stop Mio from falling in the water, but ends up falling himself and Mio jumps in to help him out. After reliving the same day, that evening, he calls Tetsu reporting a fake fight in order to keep him away from Shadow Mio. He sets up his phone outside the house and has it recording. In the morning, he shows the footage to Mio, explaining that on the video she can see a Shadow, that is there to kill Mio. Shinpei reveals he knows that Ushio saw her Shadow too and Mio then guesses that the Shadow may have killed Ushio. Mio states that Shiori saw her shadow too and Shinpei decides to go alone to Kobayakawa's place. As the Koba Mart is closed, he meets Shiomi, who decides to check on the Kobayakawa family. They enter their house to find the TV running and the table full of untouched food. While Shiomi searches for the family, Shinpei notices black strains and realizes its the marks left by the Shadow. He goes on the second floor to look for Shiori, but as he notices a flash and Shiori appears behind him producing another shadow, he figures that she is a Shadow and that he had been afflicted by shadow sickness at the funeral. However, Shiomi comes and Shiori decides to run. Shinpei then goes to look for the woman with glasses, but is unable to find her.
Shinpei then returns to Kofune's Diner, where Tetsu comes, but as he acts differently, Shinpei realizes he isn't the shadow Tetsu. Tetsu then gives him Ushio's phone, who told him to give it to Shinpei if something where to happen to her, day before she died. Sou then comes and Shinpei decides to tell him everything. They decide to go to the Hiruko shrine tomorrow, during the Summer Festival, as being crowded would be safer. They go the next day, but before they go meet the priest, Shinpei sees Ushio and runs after her. He ends up following her to the beach, where he sees her standing in the water. Initially, he believes she is a shadow, but as she can't remember her death, her way of talking and behaviour, make him feel she may indeed returned from death. Ushio then heads at the festival, where Shinpei makes her to hide since everyone believe she is dead. He explains she can't meet with her friends and tells her to stay there as he heads to join them. However, on his way to the shrine, Shadow Mio appears in front of him. She knows he filmed her and wonders how he knew she would be there. As she captures him, a shadow Shinpei comes, who makes a flash, making Shinpei realize they will get his most current memories. Shadow Shinpei explains that Shinpei is able to loop, but can't do it willingly, so he tells shadow Mio to not kill him. Shadow Shinpei heads to join Shinpei's friends and while Shinepi tries to stop him, Mio breaks his arm, stating that its pointless to struggle as soon Mother will wake up. Hizuru then appears and blows Mio's head with a shotgun and then shoots her shadow and kills her.
Hizuru introduces herself as Ryunosuke Nagumo, and explains she is there to save Shinpei. Seeing a shadow coming, Hizuru pulls Shinpei to the side and they see Ushio running and heading uphill. Hizuru explains that shadows true forms as the flat shadows on the ground, who don't like to be stepped on. The shadows eat human data, but to get the taste, they have to consume the human. As they notice a flash uphill, Shinpei wants to go save Mio and asks Hizuru for help. Heading up, Shinpei finds a massacre, where the shadows had killed numerious humans. He sees Tokiko being killed by a shadow and shadow Sou killing Sou, who tried protecting Mio. A large shadow grabs Shinpei and recognizes his right eye as the eye their Mother lost long ago, which allows him to control time. The shadow explains that just like in video games, the hero can restart from a save point, but for the Demon King to win, he must cut out the electrical power. It then tells Shinpei to observe him as he cuts the power. Shinpei tries to get to Mio, but the shadow consumes her, along with the other humans, offering them as meal to their Mother, who then appears in the sky. Hizuru apologizes, saying she should have believed the message sooner, but Shinpei states its not too late and ask her to shoot him in the head as he will return to July 22nd. The shadow tries to consume them, but Ushio punches it. Hizuru then shoots Shinpei, who starts floating and sees the island being consumed by shadow and Mother noticing him. As he starts returning back in time, this time he clearly hears Ushio, who tells him that his power has a limit and that everyone dies at the festival.
Shinpei awakens on 22nd, already on the island and after he met Mio and she pulled him out of the water. Later he thinks of what he can do and realizes that each time his returning points moves ahead. Because of this, he realizes he can't keep failing as eventually he will reach a point where Mio and the rest start dying and he will never be able to save them. Shinpei decides to do everything the same and goes to the funeral, where he have same conversations. He tells Shiori that she met a Shadow and if he does again, she needs to run. A bit later, Shiori's mother, Asako asks him what he meant by shadow, but Shinpei notices they are shadows already and explains its something Mio's grandmother had told them when they were young. Shinpei recalls that when Shadow Mio killed him, she had white panties, but today Mio is with blue and white stripped panties. He asks her if she was with white panties yesterday and even though she finds it strange, she confirms, making him realizes she was copied yesterday. Proceeding with the funeral and after the crematorium, Shinpei asks around people if they know about shadow sickness and if they know who Hizuru is. Alain tells him that Hizuru is an old friend and gives him a note she gave him as contact info. Seeing the note, Shinpei realizes its the code from Ryunosuke's Adrift novel. Solving it, he calls the phone, but Ginjiro picks up, who asks him to head to the funeral hall. There, he tells him to stand still and shoots at Shinpei's shadow on the ground to see if he is human or shadow. Confirming he is a human, Ginjiro calls him to the fourth battery. There Ginjiro explains that to solve the code, you must know that Hizuru and Ryunosuke are the same person, but that is only he knows or if a shadow had copied Hizuru, however, its interesting how a human would know it. Hizuru shows up and to reveal his name as she told him, Shinpei asks for an autograph saying he is Shinpei Ajiro. After giving him the autograph, Hizuru tells him to correct her if what she say is false. Hizuru then notes that he didn't knew who she was in the boat and the only way he to know her real name is if she told him. Hizuru notes that this isn't the first time he experienced July 22nd and repeated in multiple times. This would mean, he is a time traveler. Shinpei starts crying and confirms.
Shinpei reveals his notes about the upcoming events with the shadows. Hizuru believes him and explains fourteen years ago, her family was killed by a shadow. Ginjiro states that shadows are going after all family members, making Shinpei realizes why they came after him and Mio, but then starts to worry about Alain, however, Hizuru states she already killed Alain's shadow. Ginjiro explains that once the shadow that copy a person is killed, that person gains immunity and they can never copy the person again, which is also the case for him. Shinpei asks for help to deal with shadow Mio, but Hizuru wants to do something first. Shinpei guesses its the Kobayakawas, but explains she saw Shiori at the festival, so she must had escaped Hizuru and requests to join them to help. They head out to the Kobayakawas, where Hizuru tells Ginjiro and Shinpei to wait outside. Seeing her listen to a recording, Shinpei wonders what is going on and Ginjiro explains that Ryunosuke doesn't have Hizuru's memories. Shinpei guesses that Hizuru has dual personality, and Ginjiro confirms its something like that. He explains that fourteen years ago she found her dead brother with bite marks, but they where only a distraction from the strangle marks on his neck. But no one believed her it was a murder. Ryunosuke texts them that he killed Asako and Tetsuo, but Shiori went on the third floor. Since Shinpei may be correct, they are moving to Plan B. Soon, Ryunosuke texts them that Shiori would escape from the window and as she does, Ginjiro starts shooting at her with a nail gun, but she managed to escape past him. Waiting at the corner, Shinpei jumps and tackles her. She attempts to escape and bites him, but Ginjiro pierces her three times and tells Shinpei to let her go as once a shadow is pierced three times, it can't move. Shinpei asks her if she killed Ushio. After she was asked again by Ryunosuke, Shiori confirms. Shinpei gets angry and asks what their goal is. Shiori reveals that the end is coming and she was trying to escape with her family. She states she is reborn and is the real Shiori now, and wants Shinpei to become a shadow and join her as her big brother. Ryunosuke then kills Shiori, stating that if you talk to a shadow too long, you will get misled. Ryunosuke then introduces himself as Hizuru's younger brother and explains that he appears when Hizuru is forced to do things she dislikes, like interviews. After its revealed that Shinpei is fan or Hizuru's novels, Ryunosuke states that wasn't in Hizuru's notes, but he then punches himself and Hizuru takes over, stating they went off topic. They exchange phones and Hizuru tells Shinpei to continue doing what he would normally do and be their observer while shadow Mio appears. They go the Kofune's house and as Shinpei enters, he sees Mio with a bloody knife, however, it turns out that Mio was trying to cook and had cut herself while cutting onions. He confirms that she isn't a shadow by stepping on her shadow and tells her to go wash her face, while he makes curry. He then hears stomach growling and guesses that Mio is quite hungry, but as he turns, he sees Ushio, who confirms she is hungry.
Shinpei is shocked to see Ushio there as she should have appeared at the festival. Ushio explains that Shadow-like monsters appeared at the festival and killed everyone, making Shinpei realizes she looped with him too. He proceeds as normal and while Mio and Alain are away, he sends Ushio to his room, where he later brings her curry. There, he is prepared to kill her, but first asks her how she got here. Ushio explains she awakened at Omoto beach, but made sure no one saw her as she is being seen as "monster". Shinpei touches her shadow, making Ushio startled at it tickled her. Shinpei recalls how she decided to leave for Tokyo as he loved Ushio and couldn't continue being her step-brother. On his last day at the island, Ushio wanted he to make her curry, but he told her next time. Shadow Ushio comments that is glad she had the chance to eat his curry again, causing Shinpei to decide to not kill her. He tells her about Mio's shadow, but explains she haven't entered the house before. Soon, Mio comes to pick up the dishes and Ushio hides under the blankets. Mio leaves, but returns a few seconds later, surprising Shinpei as she almost saw Ushio. However, Shinpei notices that Mio is in her school uniform. Shadow Mio attempts to kill him, but Ushio protects him with her body. Mio stabs Ushio's shadow, wounding her. Knowing they don't stand a chance, Shinpei opens the curtains and challenges Mio, but she asks Ushio why she protected Shinpei. Ushio explains its because she loves him. Mio starts saying that she is dead and attacks Shinpei, but Ginjiro blows her head through the window and Shinpei then stabs her shadow. As she dies, she tells Shinpei that she also loves him. Hizuru arrives and wants to kill Ushio, but Shinpei stops her and instead asks her to save her as she saved him twice. Hearing her voice, Hizuru realizes its the same as the message she got. Outside, he helps her with her wound and shows her the message, where Ushio asks Hizuru for help and that only Shinpei Ajiro can save them, but Ushio has no memories of it. As Mio knew they killed Shiori, they wonder how they know it, however, Hizuru decides to leave, explaining that if he insists on sticking with Ushio, it would be too dangerous as they don't know when she may turn against them. Before leaving, Shinpei tells Hizuru that Mio killed her at 3AM the next day near the shrine and to be careful as they may send a replacement.
The next day, Shinpei proceeds as normal and goes to work at the restaurant. After getting Ushio's phone from Tetsu, he leaves with Sou, who tries to tell him something about Ushio's death, but Ushio reveals herself and guesses its the strangle marks. Sou is shocked and they explain everything to him. Shinpei then gives Ushio her phone, who sees the password was changed, but her fingerprint unlocked it. She then finds a video from the morning on the day she died. Watching the video, they see Ushio and her Shadow Ushio on it. Ushio tells him that Shadow Ushio is on their side and continues to explain how she met her Shadow and formed a plan to save Shiori. When the video ends, Shadow Ushio regains her memories and abilities and decides to replay them the memory of how Ushio died. She transports Shinpei and Sou on the private beach on 21st. They witness how Shiori is being dragged underwater by her Shadow and Ushio and her Shadow trying to save her. They manage to take Shiori from her Shadow, but Shadow Shiori then strangles Ushio and captures Shadow Ushio. She attempted to fix the faulty Shadow, but Mio and Sou came and she pretended to be the real Shiori, while erasing the real one. While Mio carried Shiori, she grabs Shinpei's arm, surprising him, thinking that was just a memory and they couldn't interact. Shiori then turns to Heine, who states she found him and won't be letting him go. Shadow Ushio ends the replay and Shinpei sees a mark on his hand where Heine grabbed him. Shinpei decides they need to investigate the old clinic.
They go to the old clinic and while looking around, they find an old wood Hiruko statue. Shinpei notices a crack on the wall and asks Ushio to go, who then sees the wall is a secret door but it needs a key. Shinpei figures the Hiruko statue looks pregnant and Ushio scans it, and copies the key from inside. As they open the secret door, Ushio tells them she feels a shadow down below and has a bad feeling. As they go down, they see its an old tunnel dug during the war. Shinpei asks Ushio to prioritize protecting herself and Sou to protect her as well. He explains that if he dies, he will loop, but if Ushio dies first, she may not loop back with him. Heading towards the shadow, they see a baby-like shadow, who appears to be deaf and blind, but manages to smell them. The shadow jumps on Sou, but Shinpei manages to pin it with his nailgun and Ushio kills it. Ushio explains that the first shadow she felt is still down the tunnel and they continue. They hear a gunshot and end in a natural cave, where they get surrounded by baby-like shadows. As they fight them back and try to escape, Shinpei notices that the shadows are only attacking Ushio. Once they manage to escape, he sees that Ushio isn't well and her wound from Mio haven't disappeared. Ushio then explains that she needs to copy the original to restore the lost data, but as original Ushio is now ashes, she can't heal the wound. Tokiko then appears, thanking them for bringing the defective product, Ushio. Shinpei shoots at her shadow to pin her, but Tokiko laughs and reveals she is human. Having no choice, Shinpei decides they to surrender, figuring that they won't hurt Ushio right away, he wonders if she will take them to her father. As they follow her, she takes them to Hiruko, who Shinpei recognizes as Heine. Tokiko explains that Hiruko likes to be called Heine, and to looks like Heine, the first person she copied. She reveals that lately Heine had issues with walking and needed a body replacement. Heine then transforms into Shiori, making Shinpei realize Heine and Shiori are the same shadow and its Heine who killed Ushio. Tokiko explains that around four people die per year on the island and they feed the dead to Heine, which is something her family have been doing for generations. The nurse Negoro brings two coffins, one of which is Ushio's body and Tokiko explains how they burned a fake body and that she didn't knew Ushio will die, but it was her fault for going against the shadows.
As Heine eats the first body and turns to eat Ushio, Shinpei asks Shadow Ushio to print him a nailgun. As she does, Shinpei shoots and frees Ushio, who goes and retrieves Ushio's body. Heine sends Negoro after them, but Ushio kills her. Shinpei gets close to kill Heine, but the shadow parent appears behind him and cuts Shinpei's fingers along with the nailgun. The shadow has Mio as a hostage, Tokiko states they didn't agree for them to touch Mio, but the shadow states they will all die tomorrow anyway, so it shoots Sou and Tokiko. Heine rips out Shinpei's right eye and starts to corrode Ushio to reprogram her, however, Shinpei's eye returns back to him. The shadow states that Shinpei's right eye overlooks the flow of time from a higher dimension and observes multiple parallel worlds. He grabs Shinpei and tells him he has the power to make the world he observes into reality, and right now he is rendering this world. However, he haven't mastered that power and he is only able to access it when he lose sense of himself in death. So they have to keep him alive until the very end. The shadow then crushes Mio's skull, killing her. The shadow intends to keep Shinpei there until tomorrow ends. Shinpei realizes he won't be able to loop and fails his promise.
Tetsu and Hizuru show up and Hizuru shoots the shadow in the head, freeing Shinpei. She then tries to kill Shinpei, but the shadow protects him and kills Hizuru. However, Shinpei takes out a poison from the poison clinic and drinks it. As he dies, he promises to do this as many times as necessary until he beats them and loops back with Ushio. He wakes in front of Hizuru, the moment she guessed he is a time traveller and as Ushio appears next to him, he confirms and states they just returned from the future.
Shinpei tells Hizuru everything and believes their mistake was that they all acted separately. Hizuru agrees to work together this time. Shinpei normally wants to go directly for Heine, but they don't stand a chance against the four-armed shadow. Ushio suggests they go after Shiori as she believes she can erase her. While gathering at the Kobayakawa's and Hizuru entering to kill them, Ushio reveals that she can keep her scanned data from previous loops and prints a new nailgun for Shinpei. To their surprise, Hizuru is throw out of the window. She tells them to run, but the four-armed shadow kills her. Heine as Shiori comes and states that ever since she touched Shinpei and left him that mark on his hand, she can easily find him. She also reveals she can also loop and had been going after him since their eyes met on the summer festival. After the shadow kills Ginjiro and is about to capture Shinpei, Ushio beheads Shinpei and scans one of the arms of the four-armed shadow.
While they are looping, Ushio reveals that the shadow had no data and its empty, but kinda smells like Heine. Shinpei and Ushio then end up in front of their house, but as its raining Shinpei finds it strange. He then sees Hizuru, who is younger. As he enters the Kofune restaurant, he realizes this is Hizuru's memory from fourteen years ago. He hears that Hizuru made a new friend and is then taken to the Hashigata old clinic in the mountain, where Hizuru meets up with her new friend, Heine. Shinpei and Ushio observe Hizuru and Heine, who spend time together. They learn that the four-armed shadow is greed incarnate and is called Shide. One day, Heine loses control due to her hunger and ends up killing Ryunosuke. As Hizuru finds them, Heine regains control and states she didn't do it, causing her to burst and blow out her eye and sends Ryunosuke's data to Hizuru. Heine runs and two stray shadows appear, but Ginjiro protects. The other shadow copies Ginjiro, but Ryunosuke takes over Hizuru and kills the shadows. Later Hizuru leaves the island and Heine promises to kill her when they meet again.
Shinpei loops back while they were heading towards the Kobayakawas, but stops Hizuru and calls off the mission. They go to the elementary school, where they call Sou, Tokiko, Mio and Tetsu and Ushio plays her memory of the past loops to them. Hizuru believes that the shadows will be coming after Shinpei and since Heine knows where he is, they can prepare and plan where they want to fight them.
Shinpei speaks in front of their group. He reveals that his life have been a mistake after mistake and he regrets many things, however, he decided that if he feels he will regret something, he will try to avoid it, even if it means to run away. He wants to inherit Ushio's will to fight the shadows and to not let the summer festival repeat. He can't guarantee them that they will win, but can't tell them to run if they are afraid. He doesn't want to feel he forced them to fight with him, but asks them to fight alongside him. One by one, they all accept, however, Ginjiro who had been scouting, had been killed and Shide taken his rifle. Shide then snipes and kills Shinpei from distance.
Shinpei awakens at his house few hours earlier and realizes he must have died. Ushio and Mio come and explain that he was killed by a sniper rifle, making Shinpei realizes they got Ginjiro. He explains to Ushio and Mio first, and then to everyone that he can only loop one more time as the time limit moves faster with each of his deaths and soon he there won't be a place he can return to.
Shinpei waits outside for Heine and Shide, but as they come and attack him, Ushio takes Shinpei and runs. While others fight them, Ushio and Shinpei manage to lure Heine and Shide to the gymnasium. There Ushio copies gasoline and Shinpei ignites it. Heine jumps to the ceiling, but Shinpei injures her. Ushio then attempts to erase Shiori since Heine was taking her form, but got distracted and Shide grabbed her and pulled her into the fire. At the same time, Shide shot Shinpei multiple times, avoiding vital organs, but ensuring his death in couple of minutes, so that he has time to kill Ushio. However, Ushio was a dummy copy and Ushio appears behind Shide and punches him and start erasing him. Heine then scans and erases the air in the gymnasium, putting out the fire and bursting the windows from the vacuum, allowing them to escape with Shide. Shinpei reveals that he is okay as he had made bulletproof vest. The group had captured shadow Mio and asks Ushio to turn her one of them.
As Shadow Mio is turned an ally, Shinpei questions her and learns that shadows like her can produce only one shadow and that shadow cannot produce more shadows. If the shadows don't erase the copied human within a week, they turn into mud. Since Seido Hishigata may know Heine's plan, Shinpei decides they to visit him. Before leaving, Shinpei asks Shadow Mio to protect Mio. Shinpei reveals she is afraid and still don't fully trust Shadow Mio, but she explains she haven't killed anyone yet in this timeline. She asks Shinpei if he has a girlfriend, but he denies. Shadow Mio wonders if he wondered why she never called him "big brother", but in that moment, the rest of the group comes and Mio pushes Shinpei to go.
Reaching the Hishigata Clinic, they see that all the furniture and items were erased by a shadow. Ushio senses a shadow and they fellow it into the morgue, but find out Ushio's body is missing. They continue a path that leads towards the Hiruko Cave and eventually find Seido being chocked by Chitose. Ushio hacks Chitose and stops her. They manage to save Seido, but he doesn't cooperate and instead wants to kill them, so Heine can trust him again. As he fails, Shadow Mio attempts to copy Seido, but sees he is immune. They see Negoro with Ushio's body, but Shinpei stops them, stating that they are just provoking them and shouldn't follow her. Shadow Mio attempts to copy Seido, but he ends up being immune. Learning that he is immune, Seido decides to talk as he no longer can achieve his plan. He gathers them and reveals that he has a list to all the patients he fed to Heine and Shinpei's parents are part of the list. They had found the Hiruko Cave and wanted to go public, but got killed by Shide. Shinpei then asks if he knows who Shide is and Seido reveals its Heine's guardian and the first child she gave birth to, Shidehiko Hishigata, the founder of the Hishigata Clinic, as well as its first director.
- The name Shinpei means "prudent, careful" (慎) (shin) and "flat, broad, level, even, peaceful" (平) (hei/pei).
- Shinpei's surname Ajiro means "network/net" (網) (a) and "generation" (代) (shiro/jiro).