Like the numbers 13 or 7 for Western culture, it is ascribed a mystical significance far outside the original definitions.
It has no readily comparable analogue to a modern Western viewer, however, though lots of similarities with the Medieval or Renaissance use of the number 9, which was considered perfect, the trinity of trinities, square of the first "real" prime (2 didn't count, sometimes, because it was even), etc.
Compare Four Is Death and its Western equivalent, the Number of the Beast; however, note that the number 108 is not always used in a negative sense as these other two examples generally are.
As you wished, the original soundtrack for Yeah Jam Fury: U, Me, Everybody!
I've been reading Fan Fictions for years now and even written a few incomplete ones on paper.