Angel of Slaughter: Episode 0

Satsuriku no Tenshi prequel
As a prison counselor, Daniel Dickens is no stranger to odd encounters with inmates. But when a particularly aggressive prisoner enters his office claiming that his session with a priest left him "fulfilled," Danny, who has led an unsatisfying life, has to know more. During their meeting, Danny finds there's little he can hide from this mysterious clergyman, and when an offer comes his way, he'll have to make a decision that will change his life forever…