Bakuhatsu Sunzen!! Tenshi no Countdown 1

Motoki is a troubled high school student. His elder sister Megumi and her lesbian partner Eika frequently have raucous sex. Eika is bisexual and enjoys tormenting Motoki, sometimes to the point of seducing him. Because she fears losing her boyfriend to her brother, Megumi is enraged by this. Even though Yuji knows that Motoki is not homosexual, his gay pal Yuji still wants to hit on him. Emi, Yuji's sister and Megumi and Eika's acquaintance, rounds out the cast. She's also bisexual, and Motoki is said to have been sexually harassed by her. Is Natsuki his key to a more rational existence?