Premieres this July. Check out the ANN article for additional information. Synopsis of the source manga from AniList:

Taro Sakamoto was the ultimate assassin, feared by villains and admired by hitmen. But one day…he fell in love! Retirement, marriage, fatherhood and then… Sakamoto gained weight! The chubby guy who runs the neighborhood store is actually a former legendary hitman! Can he protect his family from danger? Get ready to experience a new kind of action comedy series!