Miu Hiyama is a supporting character in the anime Seiren. She is a second-year student in class 2-D at Sakuragawa Higashi Girls' High School, a prestigious all-girls institution. She is a member of the school's swimming club and is described as an elite swimmer within that club. Having spent her entire education in a girls-only environment, she is notably sheltered and ignorant of the ways of the world beyond that setting. This background leads her to feel a sense of envy toward students who attend co-educational schools, as she is curious about and somewhat fascinated by interactions with the opposite sex. Her personality is shaped by this naivety and lack of experience in mixed-gender social situations. She has a known dislike for seeing boys in swimsuits, which aligns with her general awkwardness around the unfamiliar territory of co-ed dynamics. Her birthday is August 5. Her role in the series is that of a background supporting character, appearing across the various story arcs as part of the school's student body. She does not have her own dedicated arc in the original twelve-episode run of the anime, though there were reportedly plans for a future arc focusing on her that were never realized in the aired series. Consequently, her development is minimal within the main narrative, and she remains a peripheral figure whose primary function is to add color to the school setting rather than to drive the plot or undergo significant personal growth. No deeper motivations, key relationships with the protagonist Shōichi Kamita, or notable abilities beyond her swimming club membership are depicted in the series.