Butterfly-users. Androgynous teenagers. A "guy" with no memory.
It's a weird story--the kind that I like, a twisted sort of tale with no happy ending in sight. Towards the end of the game, Sera will be given one choice: To ask or Not to Ask Yoru about the butterfly mark, "he" has on his neck. There's a mini story that might or might not have occurred after the bad ending.
Story:
Having lost his memory, Sera Kaoru stops in the forest and visits a strange Western-style house. Guided by the house's owner, the boy in clothes of black, he descends the long spiral staircase to the basement. There sits a pure white maiden. Crimson eyes and white skin—a breathtakingly beautiful "girl." Sera's job is to distract her from her boredom. He reads a fairytale to her, and upon completing the peaceful job, the boy in black clothes informs him. She is the "ChouTsuki," and Sera was invited to the mansion to be the ChouTsuki's "sacrifice."
I played this while in class (I was sitting waaay in the back) so the music was turned off. I'm gonna play this again over the weekend.