Senki to Yobareta Otoko, Ouke ni Ansatsu saretara Musume wo Hiroi, Issho ni Slow Life wo Hajimeru: Innocent Days

Audre is a feared mercenary known as the "war demon." After the war was won, on the night of the peace agreement, an attempt was made on his life. Audre pretended to die in the assassination and escaped to his old hometown to live life peacefully. There he found a five-year old girl named Maria who calls him "daddy" when she saw him. Now the unmarried war veteran is suddenly the guardian of a little girl, and the strongest soldier will start a new life as the strongest parent?