"RE-MAIN" is a sports anime centered around water polo, blending themes of personal growth, teamwork, and overcoming adversity. The story begins with Minato Kiyomizu, a high school student and former water polo prodigy, who loses his memories after a car accident. Once a star player in middle school, Minato wakes up with no recollection of his past achievements or passion for the sport. As he navigates his new reality, he struggles to reconnect with his former self and the people around him.

Minato’s journey begins when he reluctantly joins his high school’s water polo team, which is on the brink of disbandment due to a lack of members. Despite his initial reluctance and lack of memory, Minato gradually rediscovers his love for the sport. Alongside his teammates, each with their own struggles and motivations, he works to rebuild the team and compete at a national level. The narrative explores the dynamics of the team, their individual backstories, and their collective effort to overcome challenges both on and off the court.

Key characters include Shūgo Amihama, the team’s captain, who is determined to keep the team alive despite its dwindling numbers; Eitarō Ōshiro, a skilled but emotionally reserved player; and Chinu Kawakubo, a cheerful and supportive teammate who helps Minato adjust to his new circumstances. The series also delves into Minato’s relationships with his family and friends, particularly his younger sister, Yū, who plays a significant role in helping him piece together his past.

The plot balances intense water polo matches with moments of introspection and character development. As the team progresses, they face formidable opponents, internal conflicts, and personal hurdles, all while striving to achieve their shared goal. The story emphasizes themes of resilience, camaraderie, and the importance of rediscovering one’s identity. Through its focus on both the sport and the emotional journeys of its characters, "RE-MAIN" offers a compelling narrative that appeals to fans of sports anime and character-driven stories alike.