Yoo Yoojin's broke and decides to expand her part-time hours to full-time, once classes end and summer begins, at the McDonald's on North Main Street. 

But before she can even wonder what could possibly go wrong, a new Burger King opens up shop right across the street (on South Main Street, to be exact) and they're losing more than half their customers to a bunch of pretty boys who can flip burgers while also flipping themselves. Admittedly, the flipping part is beyond cool so, naturally, her manager is absolutely livid. So livid, in fact, that he decides it's time to declare war.

"I want them gone." Kim Junmyeon cries out, waving a ketchup in the air with a menacing, I-dare-you-to-interrupt look. "Summer is coming and the north remembers." He whispers solemnly, his eyes glinting as if he didn't just lift a line out of that new show he's obsessed with, "We'll destroy them, even if we have to dismantle them from the inside out."

Yoo Yoojin figures it's about time she found a way to make Spent approximately 522 hours performing a variety of tasks, including espionage, fraternizing with the so-called enemies, and sabotage in order to assist management in raising sales sound good on her résumé.