K-ON! Character Image Song Series Vol. 2: Mio Akiyama is the second volume of the first season's "Character Image Song Series", featuring Mio Akiyama. The album contains the songs Heart Goes Boom!!, Hello Little Girl and Mio's version of Let's Go, as well as their respective instrumental versions. The songs are sung by Mio's voice actress Yōko Hikasa. The album was released on 17 June 2009 alongside Yui Hirasawa's version.