Tenshi Shukushi

Overview

Yui, codename: "The Killing Doll" is an matchless assassin, programmed with an emotional override that makes him little more than a puppet. Hired out by a ruthless coorporation, Yui loses control of himself whenever there's a job to be done. In the precious few moments he has to himself, he tries to build a life for himself with the guidance of a priest and fellow assassin, Miyagi.

Source: AniList