Natsu Fest Kyoku 1 "Rule" (#12 'Natsu Fest!') (夏フェス曲1「Rule」（#12『夏フェス!』） (なつふぇすきょく1「Rule」（#12『なつふぇす!』）) Natsu Fest Kyoku 1 "Rule" (#12 'Natsu Fest!')) or Summer Festival Track 1 "Rule" (#12 'Summer Festival!') is an "Insert Song" of the band BCS, produced by Pony Canyon and published on the 22th of December 2010 within the album K-ON!! Official Band Yarouyo!! ~Let's MUSIC!! 3~. The song was written by Hotaru and composed by Tom-H@ck.