- Nao Takanashi (高梨 奈緒 Takanashi Nao)
- Voiced by: Eri Kitamura
Nao, the protagonist of the story, is the adopted daughter of the Takanashi family and secretly loves her brother Shūsuke, going as far as to know everything about him to an obsessive degree.
Ten years ago, she was in a car accident which killed her true parents and caused her to lose her memory, and she had only recently learned the truth. She goes to various lengths to make sure Shūsuke becomes attracted to her, such as throwing out his non-incest porn, and becomes particularly annoyed with other girls aiming for his affections.
Her real name is never mentioned and her current name is the same as her deceased biological mother.