A harem doesn't need an air headed main character, nor does it even need love interests. A harem in anime terms is a male surrounded by more than two females or vice versa. Romance is optional. If you go ask anyone on any anime site/page/forum/etc they will tell you Index is a harem. Most of the girls he meets even have a crush on him. The reason why I like it so much is the fact the females still have a life after the events with the main character and they don't go around drooling over him/chasing after him. Other example, Ai Kora manga only(wish it had anime, but anyone who's read it knows why that's not happening), it's a harem, only 3 out of 10 girls actually liked him more than a friend and 2 of them moved on after he made it clear he wasn't interested. A harem in anime terms, doesn't need to be as ecchi as you lead it on to be, most of them are just because the fan-base enjoys it. Not to mention your 'example' of the main character falling into breasts every 5 minutes can be applied to Index, he's seen almost all the 'well-endowed' females naked or nearly naked.
Second, if this were to become a harem don't you think it would have headed in that direction years ago?
Most of the god damn story is flashbacks. Ever since the Halloween flashback ended all I've seen was Mimi coming(her background) and yet another female introduced. Chi doesn't HAVE to stop loving Mimi, but if she ends up hanging around Junior, that would categorize this as a harem.
Before you go off telling people incorrect information, make sure you know what you're talking about. I said this might become a harem because we know for a fact Bleedman is effected by Japanese culture. I'll also repeat this one more time, harems do not
require romance, all it requires, in anime terminology, is a character surrounded by at least 3 or more characters of the opposite sex. If there's a gangster character surrounded by multiple females, yes that's a harem in anime.
I apologize if anyone assumed I was speaking the other definition, I was speaking in anime terms.