13 schoolgirls are bored during their summer make-up class. When the school brass band leaves to perform at a baseball game without their bento lunches, Tomoko and the other girls persuade their math teacher, Mr. Ozawa, to let them deliver the lunches. On the train, the girls fall asleep and miss their stop. They walk back to deliver the lunches to the band, but they have spoiled in the summer heat, and all but their cymbal player, Nakamura, becomes sick.