Wondering if there's any drama where an adult suddenly becomes friend or caretaker of a teen. Or maybe something where a teacher and student develops a friendship outside school. However I'm not looking for a series where a teacher saves a new student every new episode/arc, I've seen that already.
Thanks!
Akumu-Chan
Bitter Blood (father and son relationship)
Houkago wa Mystery Totomo ni
Himitsu no Kankei ~Sensei wa Doukyonin~ (romance involved)
Kazoku Game 
Welcome to Fortune-Telling Onmyo Shop
Super Daddy Yeol
I Hear Your Vocie (contains a bit romance)
Cunning Single Lady (I'm thinking Myungsoo and Sang Wook here)
Dating Agency : Cyrano (CO- workers)
Flower Grandpa Investigation Unit 
High School - Love On (I'm thinking here the relationship between mother and son)
Innocent Man

Nobody knows (korean, just finished, the female lead is friends with a highschooler)