My theory: Hinako and her family (parents + older brother) were driving down a seaside road when their car crashed into the ocean and everyone drowned, except Hinako, who was helped to escape by one of them. Now she is suffering from severe depression and PTSD, but because this is Japan (or, at least, the drama manga version of it), mental health does not exist, so she is left to cope with her trauma on her own.
Slightly more far-fetched supplementary theory: A monster (perhaps even Shiori herself?) caused the car crash because it wasn't just Hinako who is extra tasty, but her entire family, that's why the monster let her go while it was busy eating the other three.
last edited at Aug 30, 2020 4:06AM