暗い森のサーカス (Kurai Mori no Circus)

Background
It is rumored that this song is based on actual events where a "circus" would kidnap children, amputate them, rape them, throw acid on them if they misbehaved, and make them act cheerful and happy for visitors who came to see the "show". To see the show, you had to look through holes in various tents.

Miku and others are now part of the circus. Miku is now a "deformed diva". Rin and Len have both of their heads on one body. Kaito had his brain switched with a dog's and is hinted to be a cannibal. They all hate the circus, although Rin pretends that she is happy and having fun while Len and Miku openly express their hatred for it.

This song is part of the Dark Woods Circus Series, and is the most well known song from it.