Mahoutsukai ni Narenakatta Onnanoko no Hanashi: Season 1, Episode 8

1 - 8: I'll Be Having the Complete Sauna Experience!

A freak blizzard buries Rettoran in snow and delays the start of classes, so Kurumi and friends go out to play on the frozen lake. When they decide to build a sauna, Kurumi finds a massive stone that may be more than it seems.