Before saying anything at all, just let me say do not let him watch RH Plus.
I may be a harsh critic, but that thing was just... And if you're gonna make a yaoi series about vampires, at least make it believable. It wasn't even yaoi, it was more creepy touching.
MOVING ON
Nodame Cantabile, perhaps? It's a jdrama, but it's really funny. It may also trigger an interest for classical music which is never bad to have. It's a nice mix of the serious life of a musical student and a whole bunch of crazy. It's just a classic.
Other then that, maybe Dream High. I'm not really gonna bother to explain why since I honestly can't remember what it was about, rofl. It had mild sexual content (if any at all), funny moments and music. That's basically what I remember. It's a fast and innocent watch. Thumbs up I guess.
Hana Kimi is always a safe pick. I'm not gonna bother to say why since I'm pretty sure everyone here knows why. :P Let him watch that, it's luff.
Now, I don't know how mature this 12 year old is. If he's a 'late bloomer', then I'd scratch this, but if he's mature enough I guess you could show him Bloody Monday. It's action-packed and filled with tension and suspense, yet I'm pretty sure there's nothing in it that he hasn't already seen on TV. I remember myself as a 12 year old (give or take a year :P) and I watched Criminal Minds where they killed each other with hammers. (And no Skye, that does not 'explain a whole lot'.)
Anyway, depends on his tastes in korean/japanese/taiwanese, his interests and maturity.
