This absolutely did hit me in the feels, I'm glad that they're able to be together in some way, and I got kinda teary eyed when I saw that Ko has adopted Mahiru's old hairstyle. High schooler Ko's design is pretty great.
But if I'm being completely honest, this is not a fantastic way to end it. Unless Ko's half-vampire status also brings a significantly longer life, this essentially confirms that even if they stay together Nazuna is basically doomed to watch Ko age and die as she has to fight her urges. We know essentially nothing about Ko's half-vampire status, Nazuna's status as a born vampire might as well not matter whatsoever since it seems to have absolutely no effect on the vampire rules, and we have no idea how their future goes at all.
It doesn't help that, at least based on what we saw, Nazuna was absolutely planning to just disappear and not see Ko for a very long time. She is NOT that coldhearted, and I absolutely believe that her love for him is too strong for her to knowingly hurt him like that. And as much as I appreciate two mature characters acting in a mature away, would it really have hurt to have their reunion be at least A LITTLE more heartfelt and dramatic? Yeah this dude just tracked his vampire lover to the Antarctic(?) after three years of not seeing her because she ran off despite the fact that it hurt her too, but we're not gonna react beyond "WTF are you doing here"???
I mean come on. No hug, no kissing, no Nazuna admitting that she really wanted to see him, not even any confirmation that Nazuna is gonna stop jerking him around and actually be with him now that he's proven he'll go to any lengths to be with her. BARELY EVEN ANY BLUSHING.
Honestly unless the author comes out with some sort of additional epilogue I'm just gonna headcanon that they properly get together from here on, Ko's half-vampire status dramatically slows his aging once he gets to his prime to the point where he can live for hundreds of years, Nazuna's status as a pure vampire born from a vampire and a human lets her suck Ko's blood without repercussions, and they lived happily ever after.
DUDE TRACKED A VAMPIRE WHO DOESN'T USE TECHNOLOGY TO A REMOTE HOUSE IN THE ANTARCTIC, TRAINED HIMSELF TO KEEP HER URGES IN CHECK, AND DIDN'T EVEN BLAME HER FOR JUST LEAVING WITHOUT A WORD! GIVE THAT MAN HIS GODDAMN KISSES.
Not even any real confirmation that the whole "Vampire sucking the blood of a human they love kills them" things, much less that it applies to Nazuna. This could've been A LOT better.
EDIT: Okay to be fair, the "till death do us part" line pretty clearly implies that they're gonna be together. But it's still unnecessarily vague and the situation overall lacks real impact.