قسمت 1: شش واحد با وجود نداشتن آدرس بازگشت، در جشنواره موسیقی نادر U4 Fes شرکت می‌کنند

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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)