From Bliss:

One summer day, a fifth grade boy name Susumu suddenly appear before former biker gang member now current host club host, Okita Yamamto and said that Okita is his father! Afraid of being a bad influence on his son, Yamamto transform himself into a daytime working parcel delivery man. But being a father is harder than it seems as Yamamto struggles to become a good role model for his son.