Fun Facts regarding "Blue Blue Sky":

* This is the opening theme for a war visual novel game called "Sengoku Gensokyo,"
  which is available in English on my website if you're interested.

* The beginning of the song on Expert and Hard feature long holds; Expert makes
  you twist repeatedly, Hard does not.

* The rest of the song is pretty standard fare.

* Expert has a lot of 16th stream during the chorus that is supposed to go
  partially with the background melody; it's just broken up with some lyrical
  arrows is all.