Hmm your expecting a lot from a jdrama as they usually dont do movies and shows like that (from what I have seen). It more about the journey to the romance, how bad do you want to be with that person, defining you know they are the one. Looking over my romance list (https://mydramalist.com/list/73DnmZk1)
Good morning call +Our campus days is cohab from the beginning, even though they are not together there are some moments.
5-ji Kara 9-ji Made - he is chasing her, she is running from him but he is so adorable that yeah even yamapis wooden acting doesnt ruin this )plus bonus waterfall scene..while they are not together till the end you feel the romantic tension and his overflowing love.
Buzzer Beat has some of the most romantic gestures in it but it takes a few episodes to get there Once he gets trapped in her bed room it just gushes...but this one may take too long for you.
The rest take time to set up why they are perfect for each other and set up great foundations for love and not so much romance.