Kouki Nishina, a salaryman who is suffering from mental instability, gets into an argument with his girlfriend, Sawa Kimishima, who end up killing. Kouki had lost his memory of killing her. In the meantime, Yuu Ushizawa, a temporary employee of the same company, is playing with such a quiet Kouki as a sexual toy, since she was sexually aroused while watching men suffering. For some reason, Kouki loses consciousness again and kills Yuu. A few days later, a new temporary worker, Saki Kobayakawa, arrives. She was also a woman who felt sexual excitement when she saw a man in pain. However, the love affair with Kobayakawa is also fun for Kouki, and he gradually becomes absorbed in Saki, but soon her actions start to escalate.

"Women's secret habit... that's it!? Naked body dyed crimson..."