Sou Hishigata

Sou Hishigata (菱形窓, Hishigata Sō) is a 17-year-old boy who is Shinpei's childhood best friend. He is the eldest son of Hishigata Clinic, the only hospital on Hitogashima, and is studying to become a doctor. He has a strong sense of justice and regrets that he was present at the scene of Ushio's maritime accident but was unable to prevent it. He has confessed his feelings to Mio twice in the past and was rejected.

Appearance
Sou is a young man with messy brown hair and brown eyes.

Plot
At Ushio's funeral, Sou hugs Shinpei and apologizes for not being able to help her. He offers Shinpei to punch him until he feels better, but Shinpei refuses. Sou explains that Ushio died while saving a kid, Shiori Kobayawaka, but the girl haven't spoken since then. That evening, Sou calls Shinpei and explains the rumours about his father performing an autopsy is false, but they did find strangler marks on Ushio's neck. However, given the situation and the police labelled it as an incident and only a few people know about the neck marks.