Hitomi Kashiwa

Hitomi Kashiwa was Satou's senpai during their high school years. After saying "hey, you. Join the literature club" Satou did so, However, since they were both shy, they only debated conspiracies and played cards. On the last day of high school, she confessed to Satou,that they could have been doing other things through the two years than play cards, followed by the two having sex.

As hinted in an early flashback,she had suicidal tendencies even back in high school, implied by the sentence "Would you be sad if I died?".