サイノウサンプラー (Sainou Sampler)

Background
This song seems to be about someone who becomes jealous of their friend, and they operate on the friend to gain the talent the friend has. After the surgery fails, they try to operate on themself.

This song is featured in the album VOCALO APPEND feat. 初音ミク, and two of koyori's original albums, Nostalgic Lover and World on Color. It has entered the Hall of Fame.