Sports day, or undōkai (運動会), is a very important for participation and group cohesion. In Japan they exist at every school, and each neighborhood also has one in which people of every age participate together. The event typically weaves together music, dance, and sports (the sports are often collaborative, such as a relay race). Preparation is a focus for several months, and the senior students (age 5) present a marching band show that is a highlight.
Further reading on Japanese bands and preschools: