Having gone from pampered to poor after the bankruptcy of her father's company, Youko Nishikawa struggles to drop her princess-like persona and make friends at her all-girls high school. One day, while eating alone in a nearby forest, she has a chance encounter with Futaba Odagiri, the super-energetic transfer student, and Teru Hayama, an innocent-looking girl with a surprisingly direct and sometimes mean personality. Despite their differing personalities, the three girls who all have the kanji for "leaf" in their name begin an unlikely friendship as they try to navigate through an amusing and spontaneous adventure known as high school life.

Sansha Sanyou is a cheerful, cute series revolving around three close but very different friends as they try to balance the everyday challenges that school and adolescence have to offer.