Benio Yonomori is a main character in the series Engaged to the Unidentified. The older sister of Kobeni Yonomori. She is the talented student council president at high school. Articles are written in the school newsletter about her achievements. She is presumably dedicated to her student council work as she leaves the house early to do it.
- She is an extreme siscon to Kobeni. Kobeni is Benio's younger sister who often dotes on Kobeni, to the point where she occasionally seems to be obsessed with her.
- She can be possessive of Kobeni Yonomori.
- She even claims that she would have taken care of Kobeni until she was old, and would never have allowed her to leave the house.
- Benio also has an obsession with young-looking girls such as Mashiro and even Shirayuki Mitsumine.
- She frequently invites Mashiro to the student council room for tea and cookies, or other pastries.
- Benio also has an obsession with Mashiro due to her size, claiming that she's a 'proud loli'.