Saihate no Paladin

Saihate no Paladin summary:

William is the lone human in a city of the dead. Born with vague memories of a past life in contemporary Japan where he failed to do anything useful, he is determined not to make the same mistake again, and that this time, his life will be lived. But what does that really mean? Raised by a group of the undead, William must discover what circumstances brought him to this city and these people as well as what it means to not just exist, but to live a full life.