Taeyeon regret that she lost Jessica.

Jessica have been missing her members or ex-members, and Krystal do something to make her sister happy.  

“I’m sorry Jess, I’m such a jerk, a coward, I’m a selfish person. I know, I shouldn’t do this to you, hurting you. I-” “But you did Taeyeon-ah, you hurting me” Jessica cut Taeyeon off. “What happens is happened, it’s no use if you regret it. Your regret never change anything and everything, right? Still, you never be mine.” Jessica sigh and look away from Taeyeon.