Both are about being part of a modern royal family, about living in the palace and about royal guards. Both have romance, comedy, action and politics.
In both dramas the girl is choosen to marry a prince from another country. In King2Hearts it's a marriage between North and South Korea. In Lah Ruk Sut Kob Fah a girl from Thailand is about to marry the prince of Raya.

You will get the same feeling as in both dramas the male character keeps misunderstanding the female's pure heart. So while he himself doesn't realize his own feelings, he keeps teasing and hurting her.
There is also this mean second female in both dramas

I get the same feeling watching the kids problems at school. There're gangs who pick on the weak and always feel the need to make everyone else be scared of them. Some students struggle with frienship and some other are pressured by their parents.

Both aren't school dramas where passionate teachers help solve the students problems. Some are solved between the students themselves.

In both dramas there are 2 boys struggling with their friendship. Some times they seem to be friends and some other times they seem to be opponents. These two are also the ones who aren't scared to go against the gang, but it doesn't mean that they always do. The brothership between these 2 boys are quite similar in both dramas.

The gangs in both drama are also similiar. They consist of 3 boys and are bullying the weak. The leader is actually scared that someone else in class is stronger then himself, so he always tries to show that he is the boss. The relationship between those 3 in the gang also gets tested.

So in both drama there're school, family and friendship problems.

High School - Love On adds romance and fantasy to it. Family also plays a bigger role then in School 2013. In School 2013 there is no significant romantic relationship. It focuses more on school, study, problemes between students, teachers and the parent association.

Both dramas have the same director, screen writer and lead actor, so while watching you might get the same feeling.

But that's not it. Both dramas don't focus on the romance directly. In "Pasta" it is about working in a restaurant, while in "Miss Korea" it is about working out to be Miss Korea and managing a cosmetic company.

Beside the lead actor, Lee Sun Gyun, actors Lee Sung Min and Choi Jae Hwan also acted in both dramas as supporting roles.

The sweetness and the cute romantic relationship in both movies are quite similiar. The comedy part in both are also similiar.

"Love 911" is a Korean romance, comedy & drama movie, while "Toshokan Senso" is a Japanese romance, comedy & action movie.

In both movies the male lead have a character of taking their jobs very seriously. In "Love 911" he is a fire fighter and in "Toshokan Senso" the male lead is part of a Library Force.

While "Love 911" focuses on the romance and drama part, "Toshokan Senso" focuses a little bit more on action than romance.