Cool Jessica dotes upon younger Yoona.
Yoona and Jessica who compete for the best beauty of SNSD have couple name "YoonSic". It is doubtful that frank 2 girls really get along with each other... but they get into their own world and lovey-dovey. Since they share same type B blood, maybe they have same taste.. There is a rumor that Jessica devoted a lot of attention to Yoona because her face looks like younger sister Krystal.
It's usual thing they're staring at each other or holding hands during concert. When one of them doesn't feel well, other stays close beside and treat her.
Aside from the other members, Krystal is likely to feel jealous... LOL Krystal might think Yoona as just member, but the level of YoonSic's love is much high.