Even as a music group formed through the anime, Houkago Tea Time was a big player in Japanese music during K-On's premiere run. In spite of them being the only group providing the opening and ending themes of the show and the follow-up movie, all eight of these singles peaked in the Top 5 of the Oricon charts in the week they were released in.
The second season opening theme, "GO! GO! MANIAC!", goes beyond that and manages to become the first song credited to fictional characters to reach the top of the weekly chart, while the ending theme, "Listen!", was released the same week and reached second place. Houkago Tea Time also manages to become the third female act to simultaneously place at the first and second spots of the weekly singles chart.
Houkago Tea Time also manages to be the first fictional group to top the Oricon weekly albums chart with the release of their eponymous mini-album shortly after the first season ended. They would go on to repeat this feat the next year with the full album "Houkago Tea Time II", released shortly after the second season ended.
Episode 24. Not only did they write and play a song ("Tenshi ni Fureta yo!") just for Azusa, but all the graduating members get a shot at the vocals this time, and the song is so obviously about the graduation. This doubles as a Heartwarming Moment.
Even after the series ended, Mio's poem about caramel sauce that everybody hated when she read it to her fanclub back in season 2 episode 7 makes a triumphant return as "Tokimeki Sugar", one of the best songs on the Houkago Tea Time II album. The same album has Mugi's solo "Honey Sweet Tea Time" and the finale group song "Houkago Tea Time", the latter of which can also be a Tear Jerker.
. Same thing happened at both live concerts.