MOE BLOBS. Needs moar of them!
Kidding, the atmosphere in this is brilliant and K-On was a perfect match for the song. I don't really like K-On but I found this immensely enjoyable to watch (maybe cause of the moe blobs?

) I do have to agree with MimS on the first part being slightly better than the second though. My main gripe about the second part is probably the pacing and length of the band/concert scene, it lacks some sort of dynamic action that the first part had which gave it the happy upbeat feeling of K-On. It's not really a big deal since I think you were going for more of a "dreamy" feel to end the video but perhaps stashing a few more school/friend event scenes in midst of the concert scene to level it out might have worked better since that sequence felt really long to me.
I really liked the overlays though, they make the video look shiny and so happy. I haven't seen all the videos for this group yet but I can definitely say this one is currently my favourite.
