Ayahina is one of those ships where they done the "bad boy x good girl" right without the expense of either ayato or hinami's character. I mean, the first thing that comes on your mind when you hear the name hinami is either her parents, kaneki&touka or her chimera kagune; with ayato it's his sister, father or aogiri, not who they're shipped with. They're healthy, they have agency and they barely leave place for somebody's self insertion.
Personally I feel that the bad boy x good girl trope doesn’t actually represent them? I see a lot of antis criticizing them for this actually. That this ship is toxic because of this trope, or that it’s cliched and boring.
But it’s a very superficial interpretation of their characters, in my opinion. Because the trope tend to focus on the idea of the good girl ‘saving’ the boy from falling into whatever he is and in turn she gets the thrill and excitement from engaging in things she normally doesn’t (among other things)– which isn’t Ayahina at all. Like, Hinami might have influenced him into changing for the better but she’s not the only influence, she’s only one of them (with Sachi and Kaneki being the others)– not to mention, unlike Sachi and Kaneki, there isn’t concrete evidence proving she helped in mellowing him down, though it still is a high probability. When she met him, he had already changed a little– I wrote once about how her meeting with him is similar to the conversation he had with Kaneki, and unlike the case with Kaneki, he didn’t physically hurt her despite her mentioning Touka and calling him Ayato-kun like Kaneki did. And she doesn’t like him because of his ‘bad boy’ appearance and behaviour, she’s close to him because he’s recognizable as Touka’s brother, because he’s there to support her and because he looks out for her. They’re just two lonely kids who found solace in each other and in the process, started becoming really important to each other.
There’s actually this line in the Ayahina novel story from re:quest according to this translation/summary where Hinami thinks about some ‘light that was beginning to bloom’ and like I think it’s possible that she’s referring to Ayato (possibly the rest of Aogiri as well, but considering the whole focus on Ayato and Hinami’s relationship in this story, I’d say he’s a bigger part of this light than the others are). It’s usually rare to see the ‘bad boy’ referred to as the light– it’s usually the ‘good girl’.
I love how Ishida really makes sure we known how important they are to each other, but at the same time, you’re right when you say that the ship isn’t the only thing about them. But even then, their relationship is important to both of them. I feel like it’s so underappreciated how Ishida had established a connection between them way back in Volume 3 of Tokyo Ghoul (before Ayato even appeared physically actually). I feel like these two were connected from the beginning? Like even if it’s not in a romantic sense, it’s like they’re meant to be compared because they’re both the ‘kids’ of the series (like I know we’re getting more kids now, but Hinami and Ayato are the only ones whom we actually see from young and get a chance to see them grow). So, like it’s hard to dispute the importance of this relationship (whether you see it platonically/romantically).
I get a bit of people saying that I praise Ayahina too much and I’m biased when I call them the healthiest relationship in Tokyo Ghoul because they’re my number one ship but to be honest, this is the reason why they’re my number 1? They’re healthy, they don’t steal each other’s agency (actually, I think a lot about how so far, Ayato’s the only one who’s actually brought Hinami out on a major mission) and basically, they’re just pure, which is a rarity in Tokyo Ghoul.