Jinnosuke Mudou

A middle-aged man with a bald head and a white beard. Like Rena, he is a former teacher and was her former homeroom teacher and colleague. He is the biological father of the five sisters. It was said that he disappeared and became untraceable as soon as he found out that Rena was pregnant with quintuplets, but he had been thinking about the quintuplets while traveling around the country as a lecturer. At first glance, he seems to be a gentle person, but he makes remarks that clearly seem insulting to his wife Rena and claims that Maruo, the stepfather, is not suitable to be a father, revealing his extremely self-centered personality. As a result, he has been avoiding his responsibilities as a father, which led to him being disowned by Itsuki and Maruo at the school festival, causing him to leave.