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Hello

I want to watch a Korean drama with an older male and younger female or younger male and older female

I watched [ When a Man Loves , I Hear your voice , Oh My Lady ] that's what I remember

PLEASE SEE MY LIST

http://mydramalist.com/dramalist/Peach

Thanks
The Woman Who Still Wants To Marry I do, I do Flower Boy Ramyun Shop What's Up Fox? In all of these above the older one is a female
I recommend Padam, Padam for a Older man/Younger woman relationship.
Also, one of the pairings of A gentleman's dignity is like that too, and there's also a Older female/Younger man relationship there :)
In My queen the female is older too n_n
A few more:

Ooku - http://mydramalist.com/japanese-drama/3988/ooku-arikoto-iemitsu-hen for older male/younger female
Hotaru no Hikari 1, 2 & movie - http://mydramalist.com/japanese-drama/74/hotaru-no-hikari older male/younger female

edit: I know you asked for korean, but those are still worth checking out :D

Korean:

East of Eden (long drama, but the OTP has an age gap - older man/younger girl) http://mydramalist.com/korean-drama/442/east-of-eden
Punch - younger woman/older man - http://mydramalist.com/korean-drama/1005/punch (10 years apart offscreen and most likely onscreen as well)
How about Kdrama "Saranghae"? http://mydramalist.com/korean-drama/1185/saranghae The main couple has a 14-year age gap with the guy older.
You could try Kou Kou Kyoshi it's J-Drama and not K-Drama though. Their are 2 versions of this drama a 2003 and a 1993 version both have an older man and a younger woman in a relationship. They both have a lot in common but the 93 version is better at least I think it is. I haven't really seen to many other series like these two drama's at least with an older male teacher with a female student and they actually have a relationship. It's not as light hearted as some of the drama's you mentioned so be prepared if you watch either of these. But the 2003 version will spoil certain things from 93 version because it has a few of same characters.


http://mydramalist.com/japanese-drama/2114/kou-kou-kyoushi


http://mydramalist.com/japanese-drama/790/kou-kou-kyoushi-2003
Older Male, Younger Female
- Oh My Venus
- My Love Eun Dong
- Missing You

Younger Male, Older Female
- Let's Eat
- Second Time Twenty Years Old
- High School King of Savvy
Hi 

Here are a few to come to mind::

Older Male:

Coffee Prince
Dating Agency Cyrano
Dong Yi
My Love Eun Dong
Maids
Cruel City
Ooku (the series)
Oh My Ghost
Scholar Who Walks The Night
The Greatest Love
The Painter of the Wind

Older Female:

Witch's Romance
What's Up Fox
The Lover
The Woman who still wants to get Married
Crazy For You
Last Cinderella
I Need Romance 3
Dal Ja's Spring
Kimi Wa Petto
Secret Love Affair
I do, I do 


Enjoy, Luna
I don't have any suggestions for older male/younger female, however, The Noona Romance is my favorite trope.  I've collected a bunch of titles at my blog here, https://thedramanoona.wordpress.com/the-noona-meter/
I saw someone recommended City Hall as an older female / younger male drama. It is not! The male lead is older than the female lead in both the drama and real life. That was such an odd suggestion on this list. 
king of high school. (younger male/older female). love this sweet couple so much