I Love Lee Tae Ri (2012)

Same theme about sudden change in the age of the mane character...

18y old in a body of an 30y old. And that man is Gong Yoo, what more do you need?

it's also about a younger man and an older woman - and it's just as entertaining ;)

Both are fantasy romance drama. The love stories in both drama are amazing.
The chemistry between the leads are great, and you can feel the strong love of the female lead for the male lead in both dramas.

In both drama is the story that a older woman loves a younger man. The story is funny too