The characters, oh my god the characters. They are so fucked up in a way i've seen depicted so rarely. They go way beyond "very depressed guy x guy who never loved anyone ever" and while you could boil them down to a few tropes, the level of characterization makes them feel so goddamn human they start feeling like truly unique people. I love the moral ambiguity behind them. It'd be easy to call Yaharu the victim and Jun the """"abuser"""", as he definitely has some sort of agenda behind helping yaharu out so much just because he enjoys his work and knew someone who died by suicide, and yaharu seems to just be a really miserable guy who's also a little paranoid, but it's not that easy. Yaharu can be genuinely mean sometimes because of his own insecurities, and also quite impulsive.
In the latest chapter he says some truly terrible stuff to Jun and even hits him. I'm not saying Jun is innocent on his part obviously (we'll get to it) but his reaction is just pure hostility towards someone who never even asked him for some sort of compensation. The worst thing he did is being overly touchy which i'm not denying is bad especially for someone as fragile as yaharu, but that doesn't excuse his violence. This, and even when he realizes he said offensive stuff, he mostly focuses on the regret and guilt he'll feel later instead of properly apologizing. I'm not trying to make Yaharu seem like a huge btch (especially when he forgot his meds that day) but he's a pretty self centered character due to his trauma and it should not be forgotten behind the pity we may feel for him.
On the other hand, Jun is such an interesting case because everyone can tell he's severely fucked up, and he seems to have been that way for a long time, but on the other hand even his dedicated chapters that are literally narrated by him don't seem to indicate any lack of moral compass. He seems to have an incredibly twisted vision of love and, to me, looks like despite genuinely liking some people, he also feels a profound detachement from the other people around him. And yet he's also not cruel, and the way he feels towards Yaharu cannot just be reduced to an unhealthy obsession or some kind of lust. He expressed genuine care and is ready to self reflect on his behavior if it harms Yaharu. Not only that, but the story also seems to highlight his bond with his friends, and he himself said that he eventually wants to live with them.
Deep down, what makes Jun the way he is imo is a lack of love. I think he genuinely loves the people around him, but not enough, not in a way that matters, and not the same way other people love each other. He said himself in the latest chapter that he did not feel desire but that maybe by having sex (with yaharu in that case) he could find someone to spend the rest of his life with. His relationship with Yaharu is also very familial, where he plays the parent and Y the child. But he also constantly refers to his dad's friend when talking about why he helped Yaharu so much. For me, the multifaceted nature of their relationship is a reflection of Jun's search for genuine, ever lasting love, whether it's parental, romantic or platonic.
In the end all those unhealthy traits from both characters are what make their dynamic so unique, sometimes healing, and sometimes toxic. They're fundamentally not only different, but also twisted people who at the moment need each other.