I will avoid games that are on its first releases since you asked for longer games.
Since you used Now and then as an example im guessing that when you say believable you mean a coherent story/dialogue within the game world and you are ok with fantasy,scifi,etc setups so this recommendations list are mostly games with what i consider good writing, visuals will vary.
Dark setting with post-apocalyptic theme:
hot-sand-of-antarctica
desert-stalker
If you prefer the Honey Select visuals heres a small selection of good written games with a couple hours+ of gameplay, i could recommend more but on earlier stages of development and less content:
ripples
fates-collide
lycoris-radiata
the-fiery-scion
marked-for-eternity
pale-carnations
maids-and-maidens
tainted-heritage
worlds-crossing-academy
Besides the HS heres a small selection of story driven games with good dialogues/writing:
tales-from-the-unending-void
Elvensang
The Swordbearer
Price of Power
Love Season
between-two-worlds
above-the-clouds
mad-world
If you dont mind Koikatsu based games heres the best ones, i specially recommend to try out the first 2:
How I Became the Saintess' Bodyguard
Master Rune
crimson-high
My Time with You
Since you have
My Bully is My Lover in your signature ive to mention
life-changing-choices, imo tho the story its not believable and it has poorer writing but they share world and are from the same creator.
Lastly
The Interim Domain is out there as well from same creator of Now & Then, i didnt like it, it has a good story with good characters but its very poorly written imo.
