Mao Tsuchiya is roommates with Hisashi Otomo, who is secretly gay. That's why they made 3 rules:
1. Mao must never reveal Hisashi's secret
2. Hisashi won't look at Mao as a romantic interest
3. 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 do a BL movie for their school festival project and cast Hisashi for the lead role.
(Source: Kodansha, translated)
