I'll briefly explain the couples and where they live etc :) 

Hyoyeon+Sooyoung are a couple and live together in an arts college dorm by themselves.
Jessica+Tiffany are a couple and live together along with Taeyeon in an arts college dorm.
Yoona, Yuri and Seohyun live together in an arts college dorm. None of the three are dating but Yoona and Yuri are pretty tight and snuggly etc etc ehehe..so the girls do reckon they'd make a good couple, but also Seohyun and Yoona are tight, but Seohyun's happily single. so that ship's not afloat.
Taeyeon is single.
Jeti and Taeng's dorm is directly across from Seo, Yoong's and Yuri's dorm. Hyoyoung's dorm is just down the hall. They all attend the performing arts and artistic college. 

Sunny comes in (properly) a bit later. She is hurt and broken because of a relationship that ended between her and another girl a few months ago. (I already have her ex in mind, anyone want to try guess Sunny's ex?) ;) 

anyway, enjoy the story. I don't know how long it will be but I'm pretty sure I know how it's going to end !! :D