Both are comedy high school dramas about people who moved to new cities and because of a misunderstanding were seen as the strongest guys in the area.

These two dramas both have a very similar dynamic with how the leads interact with each other. Cold older

They both have an idol moving in with a regular person. Although Love Online: Extra is bromance because of Chinese censorship but the 2 leads have really good chemistry like in HIStory: Stay Away from Me

They are both about creating an idol group. Although Top Management has some more supernatural elements and it's about a boy grouo not a co ed group.

They aren't really similar in the feels as Welcome to Waikiki is much funnier, but they are both lovable and feel good. They both are similar in the found family aspect with all the characters being unique and weird in their on way. Thirty but Seventeen has some very funny moments too yet also sometimes makes you want to cry. Just a little but you have been warned.