Who's Your Daddy?! Chisato is a divorced dad who thinks that every guy who tries to become friends with his irresistibly cute son, Riju, is just looking to take advantage of him. In his efforts to protect his adorably innocent son, Chisato often resorts to dirty tricks, such as feeding Riju's classmates snacks laced with laxatives. But, eventually, there is one guy remaining who simply refuses to give in and give up: Riju's best friend, Shunsuke. After four years of trials and tribulations, he still visits. Chisato starts to wonder whether he might actually be the "real thing," and not just a best friend.