Quote from tsuto
I don't think that is enough to label it shounen-ai. It has some undertones, but I don't see how it's obviously shounen ai.
The thing between Kamui and Keiichi is an undertone - in my opinion it's there, because of the way Keiichi treats Kamui - he's protective over him, as demonstrated during the earthquakes. Holding another guy like that - one he just met, by the way - isn't normal male behavior. This is my opinion, though. And like tsuto said, that isn't enough.
It's obviously shonen-ai because of the close relationship between Kamui and Fuma, with the intimate touches and licking and such. (And always coming so close to kissing...) I think that's the reason why it should be labled shonen-ai. Because I think the thing going on between them is enough.