"Hantsu x Trash" centers on a group of high school students who form a water polo team at their school, despite having little experience or initial interest in the sport. The protagonist, Takurou Hattori, is a first-year student who joins the team after being persuaded by his childhood friend, Natsumi Aizawa, who is also the team manager. The team is initially disorganized and lacks skill, but they gradually improve through practice and teamwork. The narrative explores their struggles, both in and out of the pool, as they face rival teams, personal insecurities, and the challenges of balancing school life with their athletic ambitions.

The series incorporates comedic elements, often derived from the team’s inexperience and the awkward dynamics between its members. Romantic subplots emerge, particularly involving Takurou and Natsumi, as well as other characters, adding emotional depth to the story. The team’s journey is marked by their determination to prove themselves, culminating in their participation in regional competitions. While the focus remains on their growth as athletes, the series also highlights themes of friendship, perseverance, and self-discovery. The characters’ interactions and development drive the narrative, creating a blend of sports action and lighthearted humor.