K-ON!! Season 2 episode #12
Sawako and the girls go to a summer music festival in the mountains, where many bands are playing in open air concerts.
With summer vacation starting, everyone initially decides to do another training camp, but instead they decide this year to go to a summer rock festival in the mountains, which Sawako conveniently has tickets for. After following Sawako's strict survival guide, the festival starts and everyone gets into it, especially Mio, although Mugi and Yui become depressed when they cannot eat the foods they want. Meanwhile, the girls shortly go separate ways to listen to different bands. While Mio gets entranced by a left-handed guitarist, Sawako enjoys headbanging to a heavy metal band far from the others. After a day of music, the girls sit under the stars, listen to the bands far away, and agree to perform at the next summer festival.