Yasunari Tsuru is a first-year Doshisha University student and a left wing player (jersey #11) on the university rugby team. He has short red hair, blue eyes, and is typically seen wearing a long-sleeved blue and magenta striped jersey above the wrists, denim jeans, a yellow belt hanging from his waist, and white sneakers with red accents.

Outwardly, Yasunari often appears mean or aloof, particularly towards teammate Natsusa Yuzuki, yet he possesses a fundamentally kind, caring, and energetically cute nature beneath this exterior. He struggles with shyness, keeping his feelings to himself, and significant self-doubt regarding his athletic rugby skills. This insecurity surfaces readily, especially when he receives advice or feedback about his performance.

His history with Natsusa is strained from early encounters; Yasunari deliberately ignored Natsusa upon his return to school and dismissed his attempts at conversation, later stating outright he didn't want Natsusa's advice. Their dynamic grows more complicated when they become roommates, a situation Yasunari finds intensely awkward. During a match, encountering a player who idolizes Natsusa distracts Yasunari, causing him to fixate on thoughts of Natsusa and make gameplay errors. This leads to a warning from the team captain about potential removal from the next game.

Following this, Natsusa confronts Yasunari about his rugby shortcomings. Through this conversation and subsequent guidance, Yasunari gains awareness of his mistakes and accepts help to address them. He works to overcome his mental hurdles, improve his play, and gradually develops a more constructive relationship with Natsusa as they navigate team experiences together. The etymology of his name reflects aspects of his character: "Yasunari" combines "peaceful" (靖) and "to be" (也), while "Tsuru" means "capital" (都) and "detain" or "halt" (留).