Big (2012)

Teacher and student relationship and the inevitable boundaries that lie ahead.
Not to mention the charming charisma of Gong Yoo. ;D

resolves around the same theme, the main guy's body serves as a vessel to someone close to the main girl.

Body-switching romantic comedies never get old! It's hilarious to see hot actors like Gong Yoo and Hyun Bin behave like they're someone else trapped inside their body.. and the parallels to the plot are naturally many.

Both dramas star Gong Yoo and focus on a student/teacher relationship

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

Althought they're different, but living inside someone eles body is what links them

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

Both have a body switch experience.
Both have 'cheesy' comedy.
Both switch between a high school student and an older guy.

Both dramas have a common plot of soul switches between siblings. In Korean Drama big both male main leads are half-siblings where one is awake and the other is in a coma and the least one who is awake has to find the meaning behind the soul switch and why it happened to reverse it. Whereas in the drama Cupid's Last Wish soul switches between brother and sister and the male main lead in sisters body embarks on journey to collect holy water from 4 monks to reverse the soul switch

18-year-old Kang Kyung Joon's spirit suddenly becomes transplanted in the body of 30-year-old Seo Yoon Jae. Seo Yoon Jae is a successful doctor and engaged to high school teacher Gil Da Ran. Gil Da Ran just so happens to be the teacher of 18-year old Kang Kyung Joon.

Both shows have one of the main characters slip into a coma, and somebody who looks just like him takes his place and wins the girl. (In Rooftop Prince, they are actually the same person. It's a time travel drama, and the one in the coma is the main character's reincarnation.)

Both Dramas are filled with cheesiness and chemistry: They give you that feeling of being in love <3

They both have mind-switching experience.

Both dramas have Body Swap
The stories somewhat turn out to be funny for both leads
Big depicts the teenage side of being a different person, But the day of becoming you both are adults

Main character abandons her fiance when she falls in love with one of her students.