The story follows a young schoolgirl named Mamiko, who experiences a bitter heartbreak after her boyfriend cheats on her. She initially drowns her sorrows by bingeing on comfort food, but soon a physical reaction forces her to the restroom...

Mamiko no Unko is a 2025 Japanese independent animated short film written and directed by Yasuteru Oono, a student at Tama Art University. The film first gained recognition on the domestic festival circuit, winning the Grand Prix at the TOHO Cinemas Student Film Festival and the Animation Best Comedy Award at the 27th DigiCon6 ASIA Awards, hosted by TBS Television.

These early wins launched the film onto the international stage. It subsequently screened at the Annecy International Animation Film Festival in France, one of the world's oldest and most prestigious animation festivals. It was also selected for the competitive short film program at the Ottawa International Animation Festival in Canada, where it competed among dozens of entries from across the world. At the Fantasia International Film Festival held in Montreal in July 2025, the film screened as part of the "Anime no Bento 2025" program and won the Silver Award in the Animated Short category.