Seido Hishigata

Seido Hishigata (菱形 青銅, Hishigata Seidō) is the father of Sou and Tokiko. He is the director of the only hospital on Hitogashima, the Hishikata Clinic.

Appearance
Seido is an adult man with short gray hair. He also wears glasses.

3rd Loop
At Hishigata Clinic, Seido is with a shadow in a wheelchair. He sees the red light in the sky and comments that Heine had recovered by consuming thousand humans.

4th Loop
Seido calls Negoro and tells her to use the policeman's, Tadashi Miura's body as today's food at 9 o'clock.

7rd Loop
Shinpei's group arrives at the hospital to see all items and furniture erased and trances of fight that leads to the basement morgue. There they continue to a hallway that leads to Hiruko Cave, and on the way they find Seido being chocked by his wife. Ushio stops Chitose and severe the connection with Heine. As Seido isn't breathing, Tokiko and then Sou, give him first aid and manage to save him. Seeing them getting to this point, Seido realizes that's why Heine wanted to kill him as she was afraid he will tell them everything. He tells Tokiko to kill them, so Heine gains his trust, but Tokiko refuses, knowing that the shadows betrayed them. Agnry, Seido manages to take the gun from Sou and shoots Tokiko. He turns to Ushio, but Tokiko then stops him, revealing she is actually Shadow Mio. As Seido refuses to talk, Shadow Mio attempts to scan him, but learns that he is immune. Negoro then shows up with Ushio's body and gives Seido a message from Shide, that thanks Hishigata family for all their help, but this is the end.

Realizing he is immune and can't achieve his goal, Seido decides to talk. He reveals that Heine wants to return to her world, which only shadows can reach and he was supposed to join her with his wife Chitose, Tokiko and Sou. Chitose calls him an idiot, but thanks him for saving her, and tells him he still can do the right think. Seido calls Tokiko to unbury a safe he had given her, and shows a list of patients who had died and he had fed them to Heine, which includes the parents of Shinpei. Seido also shows a photo, revealing that Shide is 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.

Etymology

 * The name Seido means "bronze" (青銅).
 * Seido's surname Hishigata means "Rhombus, diamond shape" (菱形).