Hiroyuki Sanada attends high school with and shares a childhood friendship with Hotori Arashiyama. He works at his family's fish shop, displaying considerable skill in seafood preparation and cooking. Raised by his widowed father, Yuuji Sanada, their relationship resembles a sibling bond marked by mutual gruffness and rare affection, reflecting Yuuji's past as a local troublemaker.

Hiroyuki maintains a congenial personality and possesses teen-idol good looks, attracting romantic attention from Toshiko Tatsuno. He remains largely unaware of her feelings due to his own longstanding secret crush on Hotori. During private moments with Hotori, he frequently indulges in fantasies about confessing his feelings but consistently struggles to muster the courage, resulting in interactions that emphasize his unrequited affection.

His practical nature emerges through responsibilities at the fish shop and daily school life. He regularly visits the Seaside maid café, where Hotori and Toshiko work, primarily to spend time with Hotori. His narrative role centers on quiet romantic tension and his dependable presence within the Maruko shopping district community, with no significant character development or changes in personal circumstances depicted in official series media.

Hiroyuki wears the standard Oya High School uniform, including a tie and school crest, paired with sneakers. His physical features include gray eyes and brown hair reaching neck length.