Can't believe not many people, I know of at least, heard of this band. Maybe I'm wrong and you have, but they just haven't gotten their own catergory in the music fandom yet. I'm gonna change that.
Think of a Japanese System of a Down meets Red Hot Chili Peppers with Ue-chan's bass lines with Flea influenced undertones, layered with Ryo's punk-nu-metal sounding guitar, Nao's average but precise drumming and pop-like vocals complimenting Daisuke's Serj-meets-Dez Fafara screams, but with a twist of unique harmony and melody flow (he dubs himself the jumping and screaming freak). Oh yeah, did I mention the video makes you feel like you're on drugs? Just without the bad trips and death from prolonged use. Combining punk, metal, funk, and even a little pop, you get these guys. In other words, you really can't catergorize these guys. They're their own sound.
I'll admit that I'm such a dork and did hear them from the Death Note ending, but it got my attention. Since I'm not a big fan of j-pop or j-rock in the ending credits of anime; I'm a newer listener of Maximum The Hormone, but like anything else, you can't pass up an opportunity to try something new. So try a little of this, it's better than drugs.
Reccommended songs: Louisiana Bob, What's Up People?, Zetsubou Billy, Bikini Sports Ponchin, and aw hell, just listen to them already!