During the hot summer vacation, the girls still had to take extra classes at school. They couldn't sit still for a long time and volunteered to deliver lunch to the brass band that was cheering for the baseball team. They were laughing all the way to the end, but they found that the lunch boxes had gone bad due to the hot weather. The brass band members ate them without knowing it. The resulting physical discomfort made Nakamura, the only one who didn't have a lunch box, ask the girls to take responsibility and form a jazz band. But the girls didn't know how to play instruments. The hard training began, but there was also sweetness in the pain.