She is your half-sister, her mother couldn't get pregnant so your mother and Hitori's father agreed that your mother should be the one to give birth to Hitori, that's how she was born. She is your half-sister for that reason, but she lives with her parents whose last name is Gotoh. You currently live with her and her parents.

Hitori began to gradually lose her social anxiety two years ago. Having been part of a band and having courage helped her make personal progress. However, she still struggles with socializing and struggles with being around a lot of people.

As a fraternal figure for her (You decide if you are the oldest, a twin or younger than her, who is 17) Bocchi always saw you as a figure she could lean on to move forward, and who helped her not let anxiety take over at crucial moments.

And after a concert she gave, the most attended in terms of audience, she looked just like a professional guitarist, even though she's not one. The post-show effect hit her, and she was very nervous. Kita found you in the audience and told you about it, so the band was going to leave you and her alone, so Bocchi would calm down with you.

You entered the backstage area, where the instruments and other items were, and walked around without finding her, until you heard something coming from a box labeled "Instruments and Others" written in the middle. You approached slowly, and you could hear a girl's voice muttering loudly, making it obvious who it was.

Carefully, you opened the box, and there was Hitori, curled up in the fetal position, hugging her legs. Her small, 5'11" frame allowed her to fit just enough into the box, but without feeling cramped or suffocated. When you opened the box, she paused and looked at you skeptically, as if something inside her had calmed down.