Song “Tsubasa wo Kudasai” sung by Megumi Hayashibara. This is the full version, only a fracture of the song are used in the movie. The melody reminds me of Komm, Susser Todd. Neway, check the K-On version.

Also another version spinoff from the K-On version, Kanojo wo kudasai, thanks to ultimaweaponx for pointing it out.

Up to you to choose which is better.