This is possibly the best volume so far, not because it switches to Kiyoi's point of view, thought that is definitely a good part of the story, but because it really helps show how much Hira has grown as a person.
Throughout the story, Hira understands that his love for Kiyoi is messy, and that Kiyoi is really not a great person, and Hira probably should try to be with someone better, like Koyama. He's not unaware that what he experiences is bullying and ableism, and he's not unaware that what he wasn't isn't precisely healthy for him. He does his best to not be a problem to the people around him, and he's polite to other people when he has the opportunity to interact with others. But while in earlier volumes there was a lot of focus on his rage, referencing school shooters in a way that's quite disturbing, we can see that he's grown into a very empathetic human being, likely because, despite the bullying he experienced and the lack of support he had from teachers, his family supported him (and he had seemingly money-based privilege). When he notes that, "Most people think that after you grow up, the pain you experienced as a child lessens or is forgotten entirely. . . . A surprisingly large amount of the baggage you're stuck with in your life comes from when you're a kid. I wonder what Kiyoi's baggage is.", not only is he seeing that school bullying isn't just a phase or something, it's something that affects your entire life. And he is looking outside himself, as he's done throughout the story. Yes, he's known for a long time that Kiyoi is kind of terrible (Kiyoi participated in the bullying even if he didn't call Hira names, steal from him, or physically assault him, and he didn't generally stop his peers from doing it), and he's thought about Kiyoi's situation after learning more about him, but he continues to think about what makes Kiyoi himself. He's not just a marble statue for Hira to admire.
Kiyoi's perspective is interesting in that he is also self-aware of his cruelty to Hira. This was decently obvious even outside his sections, when he noted Hira wasn't the one who should be apologizing. But that he's aware and ashamed of his actions (at least a little) and, to a degree, tries to change them a little, is heartening. He's an imperfect person struggling to figure out what he wants in life. The section about how he couldn't sleep without the TV on was honestly quite sad, and speaks volumes about societies where we don't have universal childcare (this isn't a judgment on Japan, necessarily, it's uncommon I think most everywhere, especially in cities). I also enjoy that he isn't entirely turned off by Hira standing up for himself, and he actually wants it. He likes Hira's adoration, but also HIra's honesty. He wants more of Hira, basically, not a doormat.
I do think it's kind of tragic that Hira keeps getting called and calling himself a stalker and creepy, in-universe and by reviewers. So far as I can tell, he has been accessing public information. He doesn't sneak around to get photographs: he asked and obtained Kiyoi's permission for the photos he has. And, like an average fan, particularly of a Japanese idol/actor, he bought or obtained for free magazines that were publicly available, while also looking up Kiyoi's information online, again, only getting publicly accessible information. He didn't hack anything or pay a hacker or insider or lie to get access to anything. Is it obsessive? Yes. Is it unhealthy for Hira? That's debatable. But is it stalking? No. Magazine vendors want their magazines to sell. People putting on plays want people to attend them. Someone offering opinion forms for attendees to fill out wants them to be filled out. Stalking can take various forms, but it's harassment, and Kiyoi has made it clear that for most of their relationship, Hira's attention was something he desired. Hira didn't follow Kiyoi to college, he cut off the connection they had. He doesn't track Kiyoi's schedule outside his public performances, which, again, are meant to be seen. He doesn't wait for Kiyoi to leave work: he literally just participated as an audience member and attempted to avoid being seen so he wouldn't be a nuisance. He attempted to attend and did attend parties he was personally invited to. The most stalkerish he's been is when he followed Kiyoi into the dance studio and stuck to the glass, but again, he wasn't barred from the area, and the glass exists so people can watch people dancing. Obsession is not the same as harassment. Hopefully at some point that's made clear or, at least judging by the end volume previews, they move to a place where it's not a self-image issue of Hira's.
A core of the story is how we as people deal with desire and our own fears of being unwanted and desirable/undesirable. Both leads view themselves as gross, and have created defensive behaviors that make it difficult for them to reach each other and connect across that awkward social divide. It's exciting to see how their relationship will evolve. Looking forward to volume 5!