Paradichlorobenzene is a harmful chemical found in mothballs, I believe.
These 2 songs basically talk about human jealousy, and how it in turn harms us like Paradichlorobenzene, I think.
[video=youtube;bC2FIqtQIZE]http://www.youtube.com/watch?v=bC2FIqtQIZE[/video]
So let's sing, let's dance
Paradichlorobenzene
So let's scream, let's shout
Paradichlorobenzene
Dogs, cat, cows, pigs, everyone
Paradichlorobenzene
So let's go mad, let's fall asleep
Until we fall apart...
I need to stop spamming this in Vindictus, lol.
EDIT: There are 2 parts before Paradichlorobenzene. Benzene and Nitrobenzene.
EDIT2:
Quote from Vocaloidism:
OwataP has mentioned on his blog that the lyrics contain hidden messages and meanings in it as there are many clues in the video. One possible interpretation is the song talking about the dark side and the selfishness of man as they become jealous of other people’s works after having their own works insensitively disregarded by others. This in turn makes such people angry as they rage against themselves and others insensitively.