Im Yoona:

She's turning 21 years old (22 in Korea).  She's been put up with a lot of stress lately with SNSD's upcoming Japanese album.  She is in a relationship with Choi Seunghyun of Big Bang. Although they seem to be an unlikely couple, they have successfully hidden their relationship for one whole year.  

Choi Seunghyun:

Choi Seunghyun is the main rapper and the eldest in Big Bang.  After trying to pursue Yoona for such a long time, he finally wins her heart.  In fact, their one year anniversary had just passed.  He is very caring and affectionate.  Because of the possibility that the fans may hurt Yoona, he decided to keep the relationship a secret.

Additional couples:

1. Yuri and Taeyang

Yuri and Taeyang are the only ones in the five SoshiBang couples to be open in their relationship.  They have been together for one year and seven months.  They hooked up Yoona and Seunghyun.  They are also responsible for the relationship of Sooyoung and Daesung.

2. Sooyoung and Daesung:

Sooyoung and Daesung have been dating for seven months.  In their relationship,  Sooyoung has been the dominant one.  To SNSD and Big Bang, they are known to be the comedic couple.

3.  G Dragon and Jessica

Jiyong and Jessica are the shy couple.  Although they aren't officially together, they are still getting to know each other.  They are known to be a shy couple because of their lack of ability to show affection in front of their own group members.  They don't show affection, but they still are interested in each other.  They secretly talk to each other on the phone and text each other everyday.

4.  Seungri and Seohyun

Seungri and Seohyun were nicknamed the "Maknae Couple" by their members.  Even though they are both the maknaes, they are complete opposites.  Seungri is more outgoing and wild while Seohyun is composed, calm, and tamed.  The two aren't an official couple.  Seungri is doing whatever he can to impress her while she does whatever she can to ignore him.