Just wanna say, I absolutely LOVE the song by Aira Mitsuki!
Anyway, on to my review:
Chara - Rainbow Gossip
It has a very ethnic feel at the beginning, it's really interesting, it makes me think of a rain forest. Then the beat comes in, and it sounds really... different. I don't know how to describe it, exactly. It sounds like some kind of tribal R&B, with synth. Also, the melody is very fun and nicely composed, and her voice is interesting when she hits higher notes. However, the end doesn't flow too well for me, the random horns just sound out of place.
Overall, 4/5.
Here's my song:
COLTEMONIKHA - Scene Killer