Rei Saiga was born with a peculiar power to see into someone's mind when he touches them. This ability caused his parents to reject him, and he was taken in by the Kujo family.

After moving out, he lives his life as a college dropout fairly normally, until Takami Kujo comes to him with an odd proposal:

The Kujo family has made their money by selling off "Merchandise" (human slaves), and they recently found one who supposedly has the blood of both an Angel and a human running through him. Takami wants Rei to find out if this is true, and as long as he doesn't hurt the boy, he can do anything he wishes to find out...