@N0Mi0 this story is actually pretty unique for a mangka, to expect much than slight difference from existing or past manga will just be a let down. Much akin to expecting any romance progression more than "we got to kiss at the end of the series". I suspect it may lie in in the production companies as well, as I've seen many light novels get their unique parts axed. Even something like the three kisses between bf/gf in "Rascal Does Not Dream of Bunny Girl Senpai" were cut out from the anime for reasons I can't find, including the last scene. Its like Japanese production companies can't stand a decent romance or find writers who can go outside the pre-defined norms.
Why does Vampire chick out herself so haphazardly? I think "I'm an insomniac who hangs out with MC who also can't sleep as well" is a legitimate answer. Also Akira takes vampire pretty well considering most depictions don't paint them as good. Not sure if I'll continue