With this manga, the only thing I'm afraid of is that it'll turn out he was stringing Nazuna along, just lying to himself about wanting to be a vampire because his life isn't fun, and he'll change his mind at the last minute. She doesn't deserve that.
I wouldn't be afraid if this were a web manga, but it's in Sunday which is a fairly mainstream publication so they might feel pressure to deliver a "moral" message with this story, about not giving up on life or whatever.