Ok, why did I not see this thread earlier? I adore my J-pop boybands.W-inds, Arashi, NewS, Super Junior, Matchy Kondo, AAA (though not really a boyband since there are ladies in it ^__^ ), and the list goes on!
KAT-TUN I have to say is relativly tame. I compare them mostly to Arashi. I mean compared to American boy bands who's dance moves are constantly grabbing their *ahem* and jiving toward sexual innuendo....KAT-TUN is most certainly not any of that. Their songs are mostly clean if not infectiously catchy.
As to the "fan service" you might be thinking more towards Tomohisa Yamashita of NewS since he did a drama/solo project with another guy which intimated toward a 'relationship' but it was all speculation and untrue much like the HYDE/Gackt thing.
I wouldn't classify KAT-TUN as immoral in the least. I mean come on they have a variety show called "Cartoon KAT-TUN" much like the Hello Project's group Mini Moni. Just great fun and super kawaii!
I hope this helps you out!
![Happy :)](./images/smilies/smile.gif)