Ballad Opera

Touma Haruto, the sole survivor of an arson case who suffers from amnesia because of it, is accidentally killed by an angel when the angel flung his devil partner (in the form of a cat) at a crow and ended up hitting Haruto. However, the dead Haruto can't go to Heaven and is apparently doomed to be a wandering ghost on Earth. The angel and devil have to serve as shinigami in order to get back to Heaven. To give Haruto a reason to live, they offer him a chance to regain his memories of his lost family and go on to Heaven by also serving as a shinigami. Haruto accepts.