Yūzan Yoshida is Haru Yoshida's older brother, sharing a strong physical resemblance marked by long, messy black hair and a habitually smiling expression. He typically wears red pants, brown boots, a light grey undershirt, and a black overshirt. Their relationship is strained. Though close during their childhood in the countryside, where Yūzan expressed pride in Haru, their bond fractured upon returning to the Yoshida family residence. Resentment grew in Yūzan over the disproportionate attention Haru received from their parents, fueled by Haru's academic talents prompting the move. This jealousy led Yūzan to distance himself, fostering Haru's distrust and avoidance. During middle school, Yūzan intervened to protect Haru from Kenji Yamaguchi's bullying, using physical retaliation that left Kenji deeply fearful. Yūzan attempts reconciliation, such as delivering their father's request for Haru to transfer schools while privately urging Haru to stay with Shizuku Mizutani for his well-being. He frequently visits Shizuku under pretenses of seeking help or companionship, relying on her to mediate interactions with Haru, which fosters a genuine, independent friendship between them. His closest confidant is Mitsuyoshi Misawa (Micchan), Haru's cousin and guardian. Their bond is rooted in mutual trust; Yūzan persuaded his father to fund surgery for Micchan's mother, Kyoko, and later entrusted Micchan with Haru's care. As adults, they share a fishing trip where Yūzan acknowledges Micchan's emotional support, calling him a "great guy" with "lots of love." Yūzan's relationship with his mother is distant and neglectful, exemplified by her forgetting his birthday and dismissing him with sweets during childhood. He recalls her resembling a "shoujo manga" character but lacks meaningful connection. Personally, Yūzan harbors a fear of girls despite a perceived playboy image, often becoming flustered in interactions. He exhibits hoarding tendencies and has a pronounced fondness for sweets, forming the basis of his friendship with Shizuku's younger brother, Takaya. In adulthood, his relationship with Haru improves cautiously. During the fishing trip with Micchan, Yūzan reflects on their growth, expressing relief that Haru found stability with Micchan's family. He demonstrates emotional maturity by valuing Micchan's guidance and acknowledging past isolation.