Chika Akatsuki and Shito Tachibana, two of the males in her class, get entirely black rings one day. She discovers their secret while attempting to warn them of their imminent demise: they are already dead, but are kept alive thanks to a contract with Zombie-Loan, a strange loan company. Of course, nothing is free, and in order to repay their loan, the guys must hunt down and kill zombies. They draw Michiru into their wild world after they discover about her "Shinigami Eyes."