the first japanese band i got into was maximum the hormone. i found them by chance. i was on jumping from band profile to band profile on myspace and came across MTH's. the name caught my attention so i listened to koi no mega lover. then the rest of the songs on their player. then to every song i could find by them.
there's also a doom metal band called church of misery that i'm really into. nice and riffy. this is my favorite song of theirs. check it out if you're into that sort of thing.
YouTube - Church Of Misery - Badlands (Charles Stalkweather)