K-On! (けいおん!, Keion!) is a Japanese four-panel comic strip manga written and illustrated by Kakifly. The manga started serialization in Houbunsha's seinen manga magazine Manga Time Kirara since the May 2007 issue, and also started a bimonthly serialization in Houbunsha's magazine Manga Time Kirara Carat since the October 2008 issue. A thirteen-episode anime adaptation produced by Kyoto Animation aired in Japan between April and June 2009. An additional original video animation episode was released in January 2010. The title of the series comes from the Japanese word for light music, keiongaku (軽音楽). This is not to be confused with the western meaning of light music—a more accurate translation might be contemporary or pop music.
K-On!'s story revolves around four Japanese high school girls who join their school's light music club to try to save it from being abolished. However, they are the only members of the club, and at first Yui Hirasawa has no experience playing musical instruments or reading sheet music. Eventually, she learns how to be an excellent guitar player. The rest of the club helps her to buy a guitar, and they perform at the school festival.