1화: 귀환 주소 누락에도 불구하고 여섯 유닛이 희귀한 U4 Fes 음악 축제에 참석

1

The six units are introduced at the Unknown Underground Unbelievable Ultimate Fes. (U4 Fes.), a mysterious music festival that takes place once every 100 years. Happy Around! receives its invitation in the mail, and although the four agree to participate, Rei notices the lack of a return address. (Source: Wikipedia)