I like those type of series too so I'll offer you a big list. lol
In random order :
* Wonderfull Life & Dekichatta Kekkon (shotgun marriage)
* Sweet 18, Goong, Delightful Girl, Choon Hyang; 1% of anything (forced marriage)
* 18 vs. 29, Queen of Reversals (already married but need to re-establish their love)
* Full House (all versions), Nagareboshi, Smiling Pasta, Lie to Me & Marriage, Not Dating (lie about wanting to get married/ making a contract-marriage)
* Paradise Farm, Cunning Single Lady, Get Karl!Oh Soo Jung (were once married or about to get married)
* Hana Yori Dango, Boys Over Flowers, It started with a kiss & They kiss again, Playful Kiss, Prince of Lan Ling, Bad Couple, Reply series ; Easy Fortune, Happy Life; Biscuit Teacher and Star Candy, Marrying A Millionaire, Unstoppable Marriage, Hotaru no Hikari, 101st Marriage Proposal (leading to marriage)