Narumi Runa

She is the younger sister of the protagonist and a first-year student at a correspondence school.
She enters the dormitory to keep an eye on her brother so that he will not be taken away by the girls in the dormitory.
She loves her brother and is always jealous of him.
She calls herself Etona Runa, to match her brother's name when he was dressed as a woman.
She is very sensitive about being praised.

"I can't believe she's so dere dere!"