[chorus | utatte mita | medley] パーラー『Me』引退祭

Hisa tweeted that and I clicked out of boredom ('cos I get bored too easily doing uni work >.>).
... turns out to be nico singers singing that nico medley (first one?).

Note: that last video is... bordering 18+, I suppose? Basically, if you don't want to see dirty (in the 18+ sense), when the song ends, pause the video and don't continue to watch.