This is the OP. Happy song, major key.
Episode 12, the arranged the OP sing in a minor key, sad. But that’s awesome! We, of course, always hear good use of the theme song during important times in a story (last ep. of Honey & Clover, for instance), but rarely do I hear the OP song arranged in such a way. Usually it’s just stuck in there, but Satoru Kousaki takes it a bit further.
There were two little bits I didn’t add in because I’m cheap and my free notation program can’t do what it’s supposed to be -_-’ (would only anal people care about how I divided the right/left hand arpeggios?)
and for fun