Ritsu looking at Sou
Ritsu Jinnai is the main female character in the manga Hibi Fukaku, the fourth short manga in the Hotarubi no Mori e tnakobon, created by Yuki Midorikawa.
History
Ritsu is the younger sister of Sou. She had been living together with her mother since their parents divorced, while Sou moved out together with their father. When they were both younger, the two siblings had a close relationship, and keeping in touch with writing letters to each other when they lived apart.