Tsuchiya Mao is roommates with Otomo Hisashi who is secretly gay; that's why they made three rules:

I. Mao must never reveal Hisashi's secret.
II. Hisashi won't look at Mao as a romantic interest.
III. Neither of them can get in the way of the other's "personal needs".

They had no problems living together until the movie club – which Mao is part of – decided to film a BL movie for their school festival project, casting Hisashi for the lead role.