I love this song and this anime as well (2nd season is better IMO)
aw man the 2nd season ties it all together so well pretty much the in Visual Novel terms the first season are the "Question arcs" and the 2nd season has most the "Answer" arcs where it all get explained, Also it has Hanyuu "Nano Desu~"Holy crap I forgot this existed. I watched the first season a few years ago and never got to watch the rest. I should get to it soon xD