I dont think he's depressed though? Hopeless, more like it. But he doesn't really fit being diagnosed with major depressive disorder
Sorry, but i think he is. I say that because i'm diagnosed with depression, and kanou's behavior is a lot like mine. Depression doesn't have to be "major", in fact it's in little things: he lives just because he doesn't feel like killing himself, he ignores his friends' attempts to contact him, he sleeps and does nothing in his free time, he has mood swings, feels down even when he looks like he doesn't, he's literally hanging on the interaction he has with the highschool boy (and now his boss) to keep on going. Before he met the boy, he didn't even have a reason to live, and you can't say that it's healthy. He could be depressed because of his heartbreak. But we also see that he has problem with accepting his personality (he thinks he's weak for others' affection, he gives too much and doesn't receive enough
-cont
etc). That means the problem is not external, it's internal. What will happen if he breakup with the boss? He himself wondered whether it would really kill him this time. That means he knows he has suicide tendencies, eventhough he doesn't act on it. A lot of stuffs in the manga points out that he's depressed. But that's just my opinion, of course, you're welcome to disagree.
This manga is truly wonderful. I can go for days talking about stuffs that i love about it, but i want to address a rather serious topic here. I saw the raws and got the idea that kanou had his happy ending, but i wish the author could've explored ways of handling depression without making it like having romantic partners is the solution. Romance isn't an answer to depression. It might be a reason for someone to keep going, but you can't expect it to cure mental illness. The way kanou perceives it, when he thought, "if i could find a new love i'd be alright" or "will my next heartbreak really kill me?" makes me sad. With or without lovers, kanou will always have difficulties with his emotions. It's just who he is, and he has to find ways to accept and deal with it independently. Mentally ill people (including me) can be happy without romance in their life. That's why i'm sad that the manga is not longer. Kanou's friendship with the highschool boy is an example of how platonic relationship can also help with mental illness, and i wish we could see it more ㅠㅠ
Aside from all that, i love this manga to pieces. I see myself in kanou, and i know a lot of readers do too. I'm truly rooting for him. I hope he finds comfort in his relationship with the boss and that it can be a motivation for him to seek acceptance within himself, so that he can be happy no matter what happens in the future.