Kawamura Mana is a first-year student at Kotaro Makimura's school and a rising star on the diving team, displaying significant talent. Her intense, prolonged training sessions focus on refining technique but disregard her physical well-being, driven by external pressures and high expectations that obscure her original, heartfelt love for diving and the water.

She has short blue or violet hair, matching blue or violet eyes, a pale complexion, and a youthful appearance, typically seen in her school uniform. Her demeanor is stoic and reserved; she rarely laughs, speaks minimally, and avoids social interactions outside necessary communication with her coach, creating an aloof aura that isolates her.

Despite her cold exterior, she possesses a contrasting romantic and imaginative inner self, harboring deep affection for the water and enjoying fairy tales, especially those involving mermaids. Kotaro discovers this hidden side as he gets to know her.

Her character arc connects to a tragic event involving Kaho Serizawa. Kotaro discovers Mana is tied to Kaho's accident, prompting his persistent efforts to break through her antisocial barriers and form a friendship to understand her.

A crucial element is a serious diving injury that threatens her future. Kotaro learns of this impending injury through experiences with time travel, shifting between different summer points. This knowledge motivates him to intervene, aiming to alter the events leading to her injury.

Her development involves gradually opening up due to Kotaro's determined efforts to befriend her. Initially resistant and dismissive of concerns about her training or life, his persistence challenges her isolation. The narrative focuses on his struggle to connect and potentially prevent the foreseen injury, intertwining her journey with the story's time travel elements.