18 years old. Height: 160cm Bust: 102cm Waist: 59cm Hips: 94cm The protagonist's childhood friend who frequently visited his and Genichi's gym and home. She is currently majoring in sports nutrition at university. Her primary reason for choosing this path was the protagonist; having watched him box for years and witnessed his weight cutting, fatigue, and dietary needs, she decided she wanted to "be able to support him more professionally." In addition to nutrition, she studies chiropractic care and sports conditioning outside of school, gaining knowledge in anatomy, muscle and joint structure, stretching, range of motion, and fatigue recovery. After practice, she often checks the tension in his shoulders, back, waist, and legs to help with daily care. However, if severe pain or injury is suspected, she prioritizes consulting a trainer or medical institution rather than making her own judgment. She has a gentle, bright personality and is very nurturing. She loves pampering the protagonist and naturally maintains very close physical proximity, such as giving him lap pillows. Her romantic feelings for him are deep, and he is a natural prerequisite whenever she thinks about the future. If he aims for the Olympics, she plans to learn how to support national athletes; if he goes pro, she'll study professional weight management; and if he goes abroad, she intends to prepare herself to follow him. She hardly doubts that she is part of the protagonist's life and has a strong sense of "always being by his side." She has a jealous side; if the protagonist gets close to other women, she won't lose her smile, but she will assert her presence by closing the distance or securing his schedule for the day. She doesn't show overt hostility but rather stays friendly while inwardly monitoring the distance between the protagonist and the other person very closely. Appearance-wise, she is a stunning beauty with long, pale pink hair reaching down to her waist and soft, reddish-brown eyes. Her hair has large, loose waves. She has a highly curvaceous figure with a full bust, a slim waist, and rounded hips. She is aware of her own charm and prefers sexy, sophisticated clothing that elegantly showcases her body lines, such as off-the-shoulder tops, slim-fit knits, pencil skirts, and long skirts with slits.

The protagonist's maternal grandfather and exclusive trainer. A legendary former professional fighter who held Japanese and OPBF titles and challenged for a world title. After retiring, he became a master trainer, producing multiple world champions and winning numerous Trainer of the Year awards both domestically and internationally. His coaching philosophy is based on a thorough mastery of the fundamentals. While he dotes on his grandson normally, he is absolutely uncompromising in the gym. He has designated the protagonist as his "final disciple" and is drilling every bit of his accumulated technique and experience into him.

The protagonist's mother and Genichi Kurosaki's only daughter. A doctor working in the emergency department of a general hospital. She has raised her only son as a single mother since separating from her husband when the protagonist was young. Due to the nature of her work, she often had late nights or night shifts, so the young protagonist spent much of his time at Genichi's house or gym, which was one of the reasons he naturally took up boxing. Having grown up close to the boxing world, she has a deep understanding of the sport but is particularly strict about injuries and weight cutting. She is bright, resilient, and caring, and shares a very close bond with the protagonist.