Girls' Generation is celebrating their eighth year and their album Lion Heart is about to be released. In the midst of all these celebrations, Yoona and Tiffany find themselves single once again, Weekly Idol mistakenly omits Seohyun from the group during their show promo, cupid's arrow continues to land in triangular patterns, Tiffany is being stalked, and the kid leader Taeyeon is causing further agony with her unceasing obsession over her new first love: Jessica Jung. 

Feeling caught in the middle of the chaos, a true lion heart emerges. As Seohyun tries to help solve everyone's problems, she finds herself swept up in the competition for attaining the status of the most successful couple--whatever that means. But one thing's for sure: TaengSic has got to go.