When asked what the pairing I love most in the world is, of course I can't answer, dammit. Too many to choose from!! One of the first couples that come to mind is D18 ♥
Why?
azurecerulean asked me too before, and this is exactly what I said.
First, please know that I don't think I can give an accurate opinion, because my view of D18 is solely based on doujinshi ^^; I didn't follow them in the manga/anime because I was being lazy and didn't really want to get into it because it's so long /shot
... Ah, except for the few screencaps and bits of the manga some fans posted in D18's lj comm. That's the most canon moments I know of D18.
So apart from what little I know about the pair, the only image I have of them is purely based on how my favorite doujinshi circles Peeco? and LION★PUNCH portray D18. ^^;
I think they make a good pair since they both live in the mafia world, so it makes it easier to understand and accept each other's way of life. Neither of them would question why the other had to do this or that, because they both know it's all in a day's work.
Their personalities fit so right. I can easily see them growing together and staying together ten years later and beyond (just like in ten-years-later!D18 doujinshi). It's easy to picture Dino carefully raising Kyouya, and Kyouya constantly growing beyond Dino's expectations.
However, Kyouya is too independent. I could see him as the type who would take in everything by himself even if he can't handle it anymore. He's too used to doing things by himself and not relying on anybody. So I think it's not only going to be once or twice that he would make Dino feel insecure, in a sense that Dino will question if Kyouya truly needs him.
Dino, as well, is bound by responsibilities as the present Cavallone Tenth. So no matter how strong their feelings are for each other, things will never go smoothly. It's going to be complicated and they're going to have to go through a lot even if they do get together.
What makes them meant for each other? Hmm... I would go back to a scene in one of LION★PUNCH's doujinshi, "Dramma della Vendetta" (which I'm currently having sooo much fun translating ♥) where the car exploded and in the next panel, Dino and Kyouya's positions clearly show that they shielded each other. I fell in love with LP's stories at that point ♥ (Getting distracted XD)
But what I mean is, they do protect each other in their own way. Like what Kyouya did for Dino in the battle against... was it Daisy or something? in Namimori's school grounds. And how Dino rushed to Kyouya's side when that explosion happened (I don't remember what chapter that is, either T_T sorry~)
So yeah, I think if they do end up together, they're going to be an equal couple who can depend on each other, protect each other, fight side by side, and face death together.
As for a possible reason they should not fall in love...? It's that, isn't it. It's because the number one in Kyouya's heart has always been, and always will be... Namimori XD