細菌汚染 (Saikin Osen)

Background
The song was uploaded to Nico Nico Douga on February 12th, 2012 gaining over 240,000 views since.

The lyrics are vague, but a common interpretation is that they song is about a girl being bullied by her classmates. The song is considered "Nightmare Fuel" due to the disturbing and menacing, yet interesting style of the 3DPV.