Simply fantastic. After having read the author's later work "Happiness", I can see a lot of the same writing here as was there, but this was written far better and didn't leave the same bitter taste in my mouth. Both had the same "the story went in a different direction to what I expected" but it was far better executed here, I'm not left wanting more or wishing that certain events didn't happen or that more chapters were spent exploring certain topics halfway through.
Slight spoilers for Happiness and big spoilers for this manga:
I'm remarkably happy that Kasuga could kiss Tokiwa towards the end, I really thought that was the moment where he would find himself unable to do it and would run back to Nakamura, so it was a pleasant surprise. Speaking of which, if you've read Happiness, you'll know that the MC basically disappears halfway through and only reappears to cap off the story - this, as I see it, is similar to the role Nakamura played here. But she doesn't come back as a deus ex machina, she comes back to complete the MC's progression. I loved how they clearly reconciled, but that she recognised that they were truly different people and told him not to come back again. I wish we had some more closure on why Nakamura tried to save Kasuga from the self-immolation, though I assume it was from some base-level recognition of the fact that he was just a "normal person", but I appreciate that she truly didn't know herself, so it fits.
Also, Aya Tokiwa is my new waifu. That is all. In seriousness, I felt that she was a fantastic addition for a "third girl" - she perfectly represented the normality that Kasuga had come to seek, and him running back to ask her out (sorry, Kouji, but you were a bit of a dick) and her immediately accepting was one of my favourite moments. There was so much opportunity to have her throw him aside once he told her everything, and I love the author for refusing to do so.
Overall, 10/10.