Aren't we just friends

Hyungwon is a student who lives with his roommate Kihyun in an three person apartment.
After the summer holidays a new student named Hoseok is coming in his class and he has to sit on the table next to him.
What will happen, and what is with the third room in Hyungwon and Kihyuns apartment.

Hey guys this is my first ff so have fun ^^.