Yuu Saigawara lives with his stepsister Reika , a shut-in erotic manga artist who uses him as a live reference for her explicit work. Whenever Reika finishes a manuscript or needs inspiration, she subjects Yuu to intense sexual encounters to ensure her art remains authentic. Despite his desire for a normal life and his friendship with a classmate, Yuu remains trapped as his sister’s primary source of creative material.

Asahi , a girl who secretly has strong feelings for Yuu , discovers that his step-sister Reika is actually a popular erotic manga artist. Without hesitation, Asahi becomes Reika’s assistant to get closer to Yuu. Driven by jealousy and pent-up lust after seeing the lewd atmosphere, Asahi transforms into a hypersexual mode just like Reika. She aggressively seduces and attacks Yuu with intense sex. Meanwhile, Reika finds out what happened and gets involved, turning the situation into a competitive, non-stop threesome where Yuu is relentlessly drained and squeezed between the two horny women.