A romantic comedy about Joo In-ah, a charismatic audit department head with a secret, and Noh Ki-joon, the department's ace who is suddenly demoted to deal with the company's scandals.

Once known as the frontman of the rock band Ambulance during his college days, Seung-min now lives a quiet life running a small instrument shop. One day, his legendary first love Bo-na, the girl he never even had the courage to confess to before she suddenly disappeared, unexpectedly reappears in his life. From that moment on, Seung-min's heart begins to race again. But as old feelings resurface, he finds himself trapped in an awkward predicament: a secret he must never let his first love discover… no matter what.