these guys are awesome! i guess they's be considered J-pop, but i'm not too sure... here're some of their songs:
Signal:
https://www.youtube.com/watch?v=XtgQIikMjC0
Yorokobi no Uta:
https://www.youtube.com/watch?v=COWMI8_fDRA
Keep the Faith:
https://www.youtube.com/watch?v=yXgZYz_5tUk
they also have a show called Cartoon Kattun, which is awesome if you guys are interested!^^