Yasuaki Tani is a first-year student at Warabi Seinan High School and a defender on the boys' soccer team. He possesses sandy-brown hair and sandy-brown eyes. As a child, he was short with somewhat curled sandy-brown hair but experienced significant growth in height over the years. Young Yasuaki was clumsy and prone to tears.

He first met Nozomi Onda after transferring to her elementary school when a group of boys bullied him at a temple. Nozomi intervened, declared she would train him in soccer, and created training sessions involving running, eating boiled eggs, and practicing ball kicks. This led Yasuaki to fondly call her "Oya-Bun" (boss), while she nicknamed him "Namek." He developed deep respect, admiration, and an unrequited crush on her. Their time together ended when Yasuaki moved away during fourth grade.

Five years later, attending Egami West Middle School, Yasuaki unexpectedly reunited with Nozomi. He arrogantly questioned her abilities, claiming his physical advantages as a boy made him superior, stemming from his lingering inferiority complex. Later, participating in a newcomers' tournament where Nozomi also played, Yasuaki observed her performance, acknowledged her skills and growth, and reconciled their friendship. Nozomi validated his improvements, recognizing his strength and dedication.

At Warabi Seinan, Yasuaki is teammates with Tetsuji Yamada and Kaoru Takei on the boys' soccer team. He maintains a competitive nature on the field, particularly as a physically committed defender. He watched the Warabi girls' team practice match against Kunogi Gakuen and attended the Saitama Preliminaries in the audience alongside his teammates and Junpei Onda.