Yasuaki Tani is a first-year student at Warabi Seinan High School and a defender on the boys' soccer team. Known by the childhood nickname "Namek," given by his friend and mentor Nozomi Onda, their bond traces back to elementary school. After transferring to her school, Yasuaki was rescued by Nozomi from bullies at a temple. She declared she would train him in soccer, subjecting him to rigorous drills involving running, eating boiled eggs, and ball kicks. At the time, he was short, clumsy, prone to tears, and lacked confidence. Their training halted when he moved away in fourth grade.

Five years later during middle school at Egami Nishi, Yasuaki unexpectedly reunited with Nozomi on the street. Eager to demonstrate his growth, he argued his physical development as a boy gave him an edge over her, displaying newfound arrogance rooted in an inferiority complex and craving for her approval. At a newcomers' tournament, he was shocked to see her competing. After the match, her acknowledgment of his improvements rekindled their friendship. This period cemented his defensive style of leveraging his physique assertively.

Now in high school, Yasuaki reunited with former youth teammates including Nozomi, Tetsuji Yamada, and Kaoru Takei at Warabi Seinan. His sandy-brown hair and eyes remain distinct, though he has grown significantly taller from his shorter, curly-haired childhood self. He maintains a fiercely competitive mindset on the field, frequently putting his body on the line during matches. Off the field, he supports the girls' soccer team, attending events like their practice match against Kunogi Academy and the Saitama Preliminaries alongside teammates. His relationships revolve around camaraderie with the boys' team and a respectful, enduring bond with Nozomi, whom he still admires and addresses as "Oya-Bun."