Nightmare is a visual kei band that plays heavy rock with a strong bassline. Much of their sound revolves around the deep vocals of Yomi. They formed in 2000, while still high school students, and began as a cover band.
The original drummer, Zanni, left in 2000 and was replaced by RuKa. In 2001, Nightmare formed their side project band Sendai Kamotsu. Sendai Kamotsu consists of the same members using a completely different image. They are famous for having a gay theme and have released three singles, two albums, and have two demos. Sendai Kamotsu also sells alot of merchandise such as baseball caps.
Nightmare was signed to Nippon Crown in 2003, and their first major single release was Believe. Their single the WORLD was used as the first opening for the anime Death Note. Raison d'etre is the opening theme song to the anime Claymore.