アオのハコ | Ao no Hako | 蓝箱 | Kutxa Urdina | Kahong Bughaw | Көк қорап | निलो बाकस | Niebieskie pudełko | Голубая шкатулка | La caja azul | Блакитна скринька | Blue Box (Oneshot)

The series focuses on Taiki Inomata, a student at Eimei Junior and Senior High, an athletics-oriented school, where he is a member of the boys' badminton team and is considered simply average. Every morning, he trains to get better early in the gym, often at the same time and place as his upperclasswoman Chinatsu Kano, the star of the girls' basketball team. Taiki quickly develops a crush on her, but is initially too shy to speak to her despite their continual alone time together. His fortunes change, however, when Chinatsu moves in with Taiki's family after her parents leave Japan to work abroad. With Chinatsu now living with him, Taiki aims to slowly develop his relationship with her as they both strive to make it to the national championship with their respective teams.

Taiki Inomata is a student enthusiastic about sports and aspires to arrive first at his school's blue-box gymnasium every day. Unfortunately, his morning smile quickly turns into a frown as he loses again and again to the girl's basketball team leader: Chinatsu Kano. Despite this, Taiki secretly likes his senior, and just the sight of her rekindles his zealous spirit.