Maelstrom (渦, Uzu) is the 5th episode of the Summer Time Rendering anime.
Shinpei is saved by a woman who was a passenger on the ferry. She identified herself as Ryunosuke Nagumo, a writer whom Shinpei admired, and said that she had come to rescue "Shinpei Ajiro". She also possessed a great deal of knowledge about "shadows". Meanwhile, a massacre by "shadows" was taking place at a summer festival. Shinpei goes to help, but his friends are killed one after another. Soon, the "shadow" swallows up everyone on the island.
Hizuru shoots the shadow Mio in the head. Shinpei recognizes her as the woman from the boat, but then notices that Mio is gone. Mio had turned into a shadow on the ground and slides behind Hizuru. She then comes out of the shadow an attempts to stab Hizuru, however, Hizuru dodges and points the gun at Mio's shadow on the ground and shoots it. Mio is surprised she managed to dodge that and due to the gunshot, she falls apart and disappears. Hizuru explains that she haven't been on the island since she was a kid, and introduces her as Ryunosuke Nagumo, and had come to save Shinpei. Shinpei recognizes the name, but before he can say anything, Hizuru pulls him to the side, stating that a Shadow is coming. They see Ushio coming and running up the stairs. Shinpei wants to go up, but Hizuru stops him, saying that that's where the Shadows are gathering. Shinpei wonders if she can tell humans from Shadows and Hizuru explains that above the shadow is just a lump of flesh in human shape. He needs to look at their feet, where their true form is the flat shadow cast upon the ground. They hate when someone steps on them and only a Shadow will move to avoid being stepped on. According to Hizuru's sister hypothesis, the Shadows scan humans with light and absorb their information. The shadows survive by eating human data, however, the data of taste requires them to consume the subject directly, which action leaves black stains behind. Hizuru notes that the shadows number had increased drastically in the last three days, no matter how many she kills and feels they may have a goal.
A flash occurs on top of the hill and Shinpei requests Hizuru's help as he wants to save Mio. He runs up the stairs and finds Tokiko, who starts crying and is then killed by a shadow. The shadow states the hour of nine is approaching and the festival is over, revealing a big pile of dead humans behind it. Shinpei freezes for a moment, but subconsciously starts counting the shadows. He sees shadow Sou who had hit Sou in the head with an axe as he was protecting Mio. Shadow Sou then proceeds to attack Mio, but Hizuru blows his hands with the shotgun. The main shadow then creates a female shadow from itself, who points a gun at Hizuru. Hizuru then sees the gun shooting and she dying and quickly dodges, but gets shot in the arm and guesses that shadow is the parent. The shadow then grabs Shinpei, looking at its right eye and he realizes it must by the eye their Mother lost long ago. He wonders why he have it, but states he can control time with it. Ushio awakens and tries to get free from Shadow Shinpei, but tells her she is a shadow like them as a human can't heal a broken arm that fast. The parent shadow states that if a "hero" dies, he can continue from a "save point" until it defeats the "Demon King", and the only way for the Demon King to win is to cut the "electrical power". He then tells Shinpei to observe him as he cuts the power. Shinpei struggles to get to Mio, but before he is able to reach her, she gets consumed, along with the rest of the dead bodies. The parent shadow offers them as meal and asks their Mother to grant him the last of her strength. Mother then appears floating in the air in a shinning red light. The parent shadow starts spreading across the island and consume anyone it touches. At Hishigata Hospital, Seido is with a shadow in a wheelchair. Looking at the red light, he comments that she had recovered after consuming thousand humans.
Hizuru apologizes to Shinpei, saying she should have believed the message earlier. Shinpei tells her its not over and asks her to shoot him in the head, saying that no matter how many times he dies, he will start over. The parent shadow prepares to consume him as well, but Ushio comes and punches him. Hizuru tells Shinpei that if he really can go back, to find her and say his name. Hizuru then shoots Shinpei in the head. Shinpei then finds himself floating in air. He sees the island is engulfed in shadow and a red girl, who then notices him as well. Shinpei then clearly hears Ushio, who tells him that his power has a limit and that everyone dies at the festival.
Shinpei returns to July 22nd, after he came to the island and met Mio. Later, Shinpei starts thinking about the situation and what Ushio told him. He realizes that each time, his starting points moves ahead. He realizes he can't keep failing as eventually will reach a point where Mio and the rest will start dying and he will never be able to save them. Meanwhile, Ushio awakens at the beach.