In the town of Saima, when summer is about to begin, a group of six high school students intend to live a secret adventure by spending seven carefree days in a ruined mining facility.

Kyoko Yoshineas Aya Chiyono (voice)
Takumi Kitamuraas Mamoru Suzuhara (voice)
Haruka Michiias Saki Akutsu (voice)
Makoto Koichias Malet (voice)
Megumi Hanas Kaori Yamazaki (voice)
Rie Miyazawaas Hitomi Nakayama (voice)
Takahiro Sakuraias Masahiko Honda (voice)
Takeo Otsukaas Hiroto Honjō (voice)
Tatsuhisa Suzukias Sōma Ogata (voice)
Mitsuru Miyamotoas Yamazaki - Kaori's Father (voice)