|Manga Debut||Chapter 1|
Kentarō is an incredibly muscular man, having apparently trained his entire life. He has short, spiky black hair, bushy eyebrows, and after training Rintarō 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.
Kentarō has been shown to care greatly for his son, taking him out to the amusement park when Rintarō was just a boy, and showed concern for Rintarō'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 Rintarō's determination to be strong like him.
His personality is shown to be quite strong-willed and is the inspiration for Rintarō's determination, not only to cope with the Hentai Syndrome, but also in his academic studies. In his own words, "A Real Man Strives to be at the Center." This is what drove Rinataro to obtain the highest scores during the mid-term exams.
While out at an amusement park with his son, Kentarō warns him to not run so much as it's dangerous. Ignoring his father, Rintarō ends up running into a nearby woman's chest, dropping his ice-cream onto her breasts. Telling his son to apologize, Rintarō's father becomes aware of his son's sudden pain. Taking him to the doctor's, they learn that Rintarō carries a disease called Henisei Tashu Ijō Syndrome, or the Hentai Syndrome for short. Distressed that his son was destined to die a virgin, Rintarō's father is forced to knock out Rintarō 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, Rintarō's father than resolves to teach his son how to handle his condition.
Taking Rintarō 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 Rintarō in the ways of Ryūha Koei Sōgetsu until his son is ready to enter high school. Warning his son to be prepared for anything, Rintarō impresses his father with the promise to never touch or be touched by a woman.
By the time Rintarō makes it to Nangokuren High School, he remembers his father's past teachings and training that resulted in him becoming strong physically and mentality.
Ryūha Koei Sōgetsu Master: As the man responsible for training Rintarō to the level of strength he has currently, it can be inferred that Kentarō is capable of similar if not greater feats as well. Due to Kentarō's greater experience, he is able to teach it much better than Rintarō as he is later seen training Rurina.
Immense Strength: As evidenced by his muscular body, Kentarō has incredible strength where he was able to split apart the land itself when making a line to keep Ayane and Rurina away from Rintarō with one punch.
Immense Speed and Reflexes: Kentarō also possesses extremely high speed and reflexes being able to make the attack that created the line between Ayane, Rurina, Rintarō, and himself before any one of them managed to react despite all three of them having powerful speed themselves.