Oniichan no Koto nanka Zenzen Suki ja Nai n da kara ne!!

Nao Takanashi discovers that she was adopted, changing how she understands her connection with Shusuke, the boy she grew up treating as her brother. Her conflicted feelings make their everyday life increasingly awkward, especially when a childhood friend returns with her own interest in him.

Family secrets, jealousy, and misunderstandings spill between home and school. Attempts to behave normally only expose the different expectations surrounding Shusuke, leaving the people closest to him struggling to make their intentions understood.