As the title says... with a happyending! the main genre has to be romance. I haven't watched a japanese drama in ages, and I feel like most romantic japanese dramas were better in 90s to early 2000s...

Koi wa Tsuzuku yo Doko Made mo

I dont love you yet

Kikazaru Koi niha Riyuu ga Atte

Shanai Marriage Honey

Kanojo wa Kirei datta 

Promise Cinderella 

5-ji kara 9-ji made
Denei Shoujo: Video Girl Ai 2018
Frankenstein no Koi
Hapimari
Nigeru wa Haji da ga Yaku ni Tatsu
Second Love
Unmei ni, Nita Koi

I prefer older doramas too. I love j-doramas from the '90s, and early 2000s also. :)

https://mydramalist.com/list/1R8av8G3

i think all the dramas in this list are made after 2014 .

hope you find something to watch

The Single Teacher Miss Hayako - really nice people in this one.