Any dramas like Birth Secret where the female lead was with the male lead (married or just together) and then something happens where they are separated. Years later, the male lead finds her again, but she's with another man now. Eventually she does remember him, and leaves the other guy to get back together with the main guy.

@fanitha 

She never forgot him in Angel Eyes. She just didn't know what he looked like because she was blind and regained her vision after he left.
Mou Ichido Kimi ni, Propose ( starring takenouchi yukata)

I'm Home ( dont get decieved by the masks, sure they look creepy at first , but this drama is amazing )
---  Sad Love Story ---  She did not forget, but does not know what he looks like now .... she was blind when w/ him, but regained her sight and is w/ another man now (his BFF) .... eventually they get back together.
--- Game Rai Game Ruk ---  She was married to him, gets taken away by her family and looses her memories of him .... they eventually get back together, as she slowly regains some of her memories. WARNING: it's a lakorn mild slap/kiss.
@rainruma

I've seen/read Sad Love Story. The ending is depressing.

I'll check out Game Rai Game Ruk, but what's a lakorn slap/kiss?
@leann123 ...LOL!!.... if u don't know than maybe it is better not to start ....
Lakorns are Thai dramas...  Slap/kiss genre is revenge driven usually full of makjang ; evil second female leads; crazy-in-love obsessed, jealous and possessive male leads ; some inconsistencies in the plot ; lots of crazy stuff and lots of things to annoy femminists .... often lots of guns and crime ... But they often also have lots of kick a** females... Slap/ kiss stands for when she insults him by slapping him, he insults her back by kissing her.
They are low-budget usually, not very high quality... so why do we watch? ... for the crazy passionate romance, usually...:P

Sounds crazy? ... It is... and they are lots of fun for those who don't mind all that ... But they are NOT for everyone.
If you want to start, there are better ones than GRGR, listed above.

Here's the  MDL Introduction article:
http://mydramalist.com/article/2014/05/23/introduc...       
@rainruma

Well I've only really seen K or J dramas, but that sound AWESOME.
@leann123 ... LMAO !!! .... I was trying to scare you off, but it seems u r intrigued ... R u sure u read all that I wrote? and read the Intro article, and saw the video in the article, especially towards the end?... 

.... Well, maybe u WOULD like lakorns!!!
If u give me specifics of your taste, or what u want tend to like , maybe I can guide to start .....  
Then again, maybe GRGR is not a bad start .... It is not one of my faves, but many people love it .... The leads have wonderful natural chemistry, not the best actors, just a lot of charm ;) .... If u don't like the trailer and want to start w/ another, let me know.

My Love Eun Dong
The Moon that Embraces the Sun
(they actually lost their memories)
The only one that comes to mind and that would almost fit that kind of story would probably be Stay With Me (Chinese drama).
Somewhat similar to Innocent Man i think in a way.. >.