Older man / Younger woman

MDL rating 9.1

Male lead actor is 12 years older.

MDL rating 8.9

Ji Sung is 8 years older than Hwang Jung Eum (they also star together in Secret Love).

MDL rating 8.7

Lee Joon Gi is 11 years older than IU.

MDL rating 8.6

Jo Jung Suk is 10 years older than Park Bo Young.

MDL rating 8.6

Park Shi Hoo is 8 years older than Chae Won.

MDL rating 8.5

Hyuk Jang is 15 years older than Park So Dam

MDL rating 8.5

Ji Jinhee is 16 years older than Han Hyo Joo.

MDL rating 8.4

Yeon Woo Jin is 8 years older than Han Groo.

MDL rating 8.4

Park Bo Gum is 6 years older than Kim Yoo Jung, very noticeable because she was 16 at the time of the drama.

MDL rating 8.4

Song Seong Heon is 14 years older than Go Ah Ra.

MDL rating 8.4

Lee Seung Gi is 8 years older than Suzy.

MDL rating 8.4

Seo In Guk is 8 years older than Nam Ji Hyun.

MDL rating 8.4

Kim Min Jong(was 40)  and Yoon Ji Yi(was 22)

MDL rating 8.4

Ji Chang Wook is 8 years older than Nam Ji Hyun.

MDL rating 8.3

Ok Taec Yeon is 11 years older than Kim So Hyun.

MDL rating 8.2

She is 29, he is 46.

MDL rating 8.2

10 years age gap

MDL rating 8.2

Jung Woo is 10 years older and  Yoo Yeon Seok is 6 years older than Go  Ah Ra. (You need to figure out who is the lead in the drama. )

MDL rating 8.1

One of the main couples is 19 years apart for real, but also about 10 years as the characters.

MDL rating 8.1

Furukawa Yuki is 10 years older than Miki Honoka, even though in the drama they are supposed to be about the same age.

MDL rating 8.0

Chung Wallace is 15 years older than Angela.

MDL rating 8.0

She is 25, he is 39.

MDL rating 8.0

Jung Il Woo is 7 years older than Jin Se Yeon and in the drama he is supposed to be older too.

MDL rating 8.0

17 years age gap

MDL rating 8.0

Nam Goong Min is 15 years older than Bang Mi Ah

MDL rating 7.9

Kim Rae Won is 9 years older than Park Shin Hye.

MDL rating 7.9

Lee Joon Gi is 8 years older than Lee Yoo Bi.

MDL rating 7.9

Huo Wallace is 8 years older than Liu Cecilia.

MDL rating 7.9

Go Soo is 16 years older than Jin Se Yeon.

MDL rating 7.9

Park Hae Jin is 8 years older than Kim Go Eun, although in the drama they are supposed to be around 4 years apart.

MDL rating 7.9

Chang Marcus is 7 years older than Liu Eugene, I add it because in the drama she acts much younger so is very noticeable.

MDL rating 7.9

8 years age gap

MDL rating 7.9

Yeon Woo Jin is 10 years older than Park Hye Soo

MDL rating 7.8

Nam Woo Hyun is 9 years older than Kim Sae Ron.

MDL rating 7.8

Yoon Shi Yoon is 14 years older than Kim Sae Ron.

MDL rating 7.8

She is 22, he is 48.

MDL rating 7.7

Male lead is 13 years older.

MDL rating 7.7

Kam Woo Sung is 20 years older than Choi Soo Young.

MDL rating 7.6

Korean movie about arranged marriage, she's a high school student, he is  her teacher. In real life Kim Rae Won is 6 years older than Moon Geun  Young.

MDL rating 7.6

Sung Hoon is 7 years older than Song Ji Eun.

MDL rating 7.6

8 Years age gap

MDL rating 7.6

14 year difference between the actors.

MDL rating 7.6

11 years age gap

MDL rating 7.6

Another teacher-student relationship movie. Yamashita Tomohisa (Yamapi) is 11 years older than Komatsu Nana.

MDL rating 7.5

The main leads have 12 years between them

MDL rating 7.4

She was 26, he was 38.

MDL rating 7.4

She was 22, he was 43.

MDL rating 7.4

Lee Joohyuk is 16 years older than Sooyoung

MDL rating 7.4

Jo Jung Suk is 11 years older than IU.

MDL rating 7.4

Main OTP is 12 years apart, actress was about 17 years in real life but in the drama, she is supposed to be about 20 or 21.

MDL rating 7.4

Oh Man Suk is 9 years older than Yoon Eun Hye.

MDL rating 7.3

Toyokawa Etsushi (male lead) is 26 years older than Eikura Nana (female lead)

MDL rating 7.3

Ryu Soo Young is 14 years older than Kim Da Som.

MDL rating 7.3

13 years age gap

MDL rating 7.2

Shin Ha Kyun is 7 years older than Jang Na Ra.

MDL rating 7.1

Takizawa Hideaki is 11 years older than Takei Emi.

MDL rating 7.0

(10 years apart) Based on the real life of mangaka Mizuki Shigeru from his wife point of view.

MDL rating 6.9

Rain is 12 years older than Krystal.

MDL rating 6.8

2nd main couple  is 16 years apart, but about 10 years in the drama. 

MDL rating 6.7

Kwon Sang Woo is 14 years older than Yoona

MDL rating 6.6

Yang Dongeun is 7 years older than Park Minyoung.

MDL rating 5.9

Lee Sun Gyun is 11 years older than Min Hyo Rin.