|Manga Debut||Chapter 1|
Rintaro's father is an incredibly muscular man, having apparently trained his entire life. He has short, spiky black hair, bushy eyebrows, and after training Rintaro for ten years has grown a similarly unkempt beard. He has only ever been seen wearing a white gi with the sleeves torn off at the shoulders.
Rintaro's father has been shown to care greatly for his son, taking him out to the amusement park when Rintaro was just a boy, and showed concern for Rintaro's well-being after the boy suffered his first incident due to his Hentai Syndrome. His dedication goes as far as to train his son for ten years in order to overcome this ordeal, and was glad to hear Rintaro's determination to be strong like him.
While out at an amusement park with his son, Rintaro's father warns him to not run so much as it's dangerous. Ignoring his father, Rintaro ends up running into a nearby woman's chest, dropping his ice-cream onto her breasts. Telling his son to apologise, Rintaro's father becomes aware of his son's sudden pain. Taking him to the doctor's, they learn that Rintaro carries a disease called Henisei Tashu Ijō Syndrome, or the Hentai Syndrome for short. Distressed that his son was destined to die a virgin, Rintaro's father is forced to knock out Rintaro when the boy was at risk of having another incident due to the doctor's appearance. Asking her to be more careful around his son, Rintaro's father than resolves to teach his son how to handle his condition.
Taking Rintaro out to the forests of Mount Fuji where he himself had trained as a child, calling it The Quiet Shore Nobody Knows. For the next ten years, he teaches Rintaro in the ways of Ryūha Koei Sōgetsu until his son is ready to enter high school. Warning his son to be prepared for anything, Rintaro impresses his father with the promise to never touch or be touched by a woman.
By the time Rintaro makes it to Nangokuren High School, he remembers his father's past teachings and training that resulted in him becoming strong physically and mentality.