But Hana deserved that...
Which is why Hana ranks way below Aya on my list, despite them being Twins and looking more or less identical - by looks she's on the fifth place, but her personality is nasty, which sends her to the pits. Hana is selfish and envious (okay, all girls are when Sou interacts with other women) but the thing is, that in my eyes she's a two-faced snake who would likely bite you from behind if it's to her benefit. I mean, she's willing to betray her twin sister and do stuff that might not only hurt Aya's feelings but also her reputation as a guard. If the hug festival resulted negatively and Sou dropped out, it would have been marked as Aya's fault since she's the team leader. In that regard, she's dangerous, because it might get worse the longer this lasts.
Aya on the other hand is a pure one at heart and even her inner horniness is tamer compared to other girls who just think about mounting him. Become friends or hold hands? How cute... well, her biggest fault is probably that she's a bit overambitious, but you need to bee if you want to be Rank #1. Miku stands in her way and since Aya is the classic honor student these two clash frequently. But Aya is professional enough to not let that get in the way of her duty as a student guard, in that regard she is highly reliable. Suzuki wouldn't have such a quiet life if not for her, so she does her job well.
Going by what we've been shown so far, Aya is shown as a responsible girl who's willing to protect her guard target whithout fail and she will take care of her team members as well. Like when Miku threatened Kaede - Aya stepped in ready to actually fight Miku. Or when Hana caused the hug fest, Aya immediately jumped up to guard Sou in case anything happened. She's be quite a nice girlfriend to have, not only by looks. Which is why I honestly think she needs time to shine and maybe the situation with Ruri that's currently going on is that time. We will see. She deserves her dose Sounium.
the original world were he was likely ignored by women.
Well he was a orphan and I his main social interaction was with some unsocial old man who ran a martial arts dojo. In that regard you could call his worldview tilted. But at the very least Sou wants to interact with others, which is a good thing. That also makes him way different from other guys who wouldn't think of actively seek interaction with females. In a sense this kind of outgoing personality is needed to wreck the stagnant status quo in the school. The girls are taught to not approach the boys and their guards also hold them back. For a reason, sure, but that makes changes hard unless it comes from the male side. And Sou might be the only male who would be able to.