It is common knowledge that nobles will do anything for power; lying, manipulation, and extortion are the usual tactics. However, one family is exempt from this generalization: House Grail, whose main tenets are truth and integrity. The youngest daughter, Constance Grail, is just as moral as the rest of her family, believing in always doing the right thing and helping those in need. However, these ideals do not help her when her fiancé cheats on her with another woman. Framed by his lover in the hope of her downfall, Constance's pleas for justice are ignored. Everyone turns a blind eye, save for one—the spirit of the infamous Scarlet Castiel—who possesses Constance and turns the tables on her accuser. However, this aid doesn't come without a price. Ten years ago, Scarlet was executed for the attempted murder of Princess Cecilia. But this was actually a setup; as blunt and harsh as Scarlet could be, she would never stoop so low as to use poison. She has no idea who orchestrated her incrimination, but Scarlet demands that Constance—as the only one who can see her—help her exact revenge on all those who wronged her!

Yuki wakes up to find herself in an unfamiliar manor, wearing a maid uniform and lying on a luxurious bed. Soon, she discovers five more girls, all dressed the same as her. This is the Ghost House, and the only way they can survive is to make it through the traps that lie in wait—deadly games full of blowguns, buzz saws, locked rooms, and weapons. It's a hopeless, terrifying situation for everyone there...well, everyone except Yuki. After all, this is her career at seventeen. Do you think that's odd? She would agree. But that's how some people are—they earn their living playing death games.

The Animal Liberation Alliance, an eco-terrorist organization, rescues a pregnant chimpanzee from an animal testing lab—only for it to give birth to a half-human, half-chimpanzee "humanzee" named Charlie! Fifteen years later, Charlie's human foster parents are finally ready to send him to a normal high school, where he makes his first friend: a human girl named Lucy. In the meantime, however, the ALA's stance has become ever more extreme, and now they're here to drag Charlie into their terrorist plot...

Yakou, a gentle human woman, works at a detective agency. Tounome is a smart and gentle invisible man. The invisible man's ability is perfect for detective work. However, the blind Yakou can still figure out where Tounome is, even if he disappears. Before they know it, the two become attracted to each other...?