In this country where it’s slightly warmer due to global warming, the hottest thing is a new female-only water sport called "sensui", where girls ride torpedo-like high-performance mini-subs called ‘MAV’s and try to knock down their opponents by shooting special water attacks at them. The sensui team at Aosaki Academy doesn’t have enough members nor do they perform well in competitions. However, the club leader Maasa is determined to turn around the fortunes of the school by enlisting a sensui ace Mito to the team. The four girls (Mito, Alice, Maasa, Rikoko) are managed by a male coach, Riku, whose dream of becoming a sensui player was dashed due to the gender restriction. Together, they aim to compete and win the national competition, the Wassergrahl.