Bromance kdramas

Although they met quite recently, the two guys immediately click with each other as if they've known each other their entire lives

As the two main characters progress with their mission of returning deserted soldiers, they get to know each other better and become a great team

A middle-aged gangster possessed a body of a high schooler and eventually becomes a parent figure/friend in the broken life of his classmate
It was heartwarming to see this poor classmate (and a few other people) finally meet a proper adult and heal

One of my favorite  kdramas !! Highly recommend it if you're looking for a comedy with a serious plot !!
The story is absolutely hilarious and the tension between the two guys is truly one-of-a-kind LOL 

(similar to High School Return of a Gangster but is a movie)
A middle-aged gangster and a high schooler switch bodies and try to figure out how to switch back

Duo consisting of a vigilante that kills criminals who weren't properly punished and his admirer who starts helping him

ML and 2nd ML used to be best friends but due to certain events, they're now on bad terms. It's both entertaining and heartbreaking to see their fights and reconciliations (to an extent).
Additionally, both of them have friends and classmates with complicated stories and relationships between each other