I've always had the tendency to discover anime late... I really like the jazzy feel to the song, and yet at the same time, it's also a song one could dance to. I was definitely surprised when I found out who the composer was for the song.
(I especially like the extended version. Reminds a little of Toad's Turnpike to be honest. 
)
Megumi Nakajima - Try Unite! (Rinne no Lagrange OP1)
中島愛 - TRY UNITE! (輪廻のラグランジェ OP1)