This song is called Unreal and it's sung by Vocaloid Hatsune Miku.
The title of this song is Yuuhi Saka. I don't know who sings it, but credit for the animation goes to youtube ...
Members of the Nico Nico Chorus are singing a remixed version of Dancing Samurai, which was originally...
Kaito and various members of the Nico Nico Chorus are singing a song. Credit for this video doesn't go to me.
Miku's decided to temporarily become a cat girl. Credit for this video doesn't go to me.
Miku's little girls are riding their tricycles and racing each other. I do not deserve credit for this video.
Luka and Miku are singing a song called Aa! Senba!. I do not deserve credit for this video.
Luka and Gakupo are singing a song called Go Google It! I do not deserve credit for this video.
Luka's singing a song called Melancholic. Credit for this video doesn't go to me.
Rin's trying to express her feelings. Credit for this video doesn't go to me.