After 10 years of staying overseas, Seo Eunbi had finally returned to Korea. She thought she ought to have her life figured out by 30. But Eunbi was single, jobless and... kind of homeless. Her silver lining, was that she had her cousin, Seo Eunkwang. It also helped, to reunite with her best friend, Park Harin. And then, there was Eunkwang's friends, Im Hyunsik and Lee Changsub, who readily welcomed her into their lives.  Together, they could figure out what it means to be 30.