K-ON! is a popular Japanese manga (comic) and animation. The second season of K-ON! was named K-ON!! (with two exclamation marks). The name K-ON implies light music in Japanese, a deviation of pop music. The story begins with how four girls of a light music club in a high school tried to save the club from being discontinued.
K-ON! started as a fout-panel comic and later adopted as animation aired on TV, original video animation (OVA) and movie. The TV anime has been very popular and widespread in the world thanks to TV networks such as Animex. There was also a Playstation Portable (PSP) game released in 2010.