After losing his girlfriend in an accident, three years later Lee Hyeonwook tries to track down her little sister, Yoon Sena, when he finds out she's struggling.

Hyeonwook keeps finding excuses to see Sena, but there's trouble when the loan sharks are hot on her trail again. ANA is in a bad spot when the president collapses.

After temporarily accepting the position of president, Hyeonwook offers Sena a position to train as a songwriter at ANA, but PD Seo Jaeyoung wants to get rid of both of them as soon as possible.

When Hyeonwook volunteers Sena for a composition contest between her and Jaeyoung, she has a hard time finding inspiration.

Hyeonwook is left to pick up the pieces when Jaeyoung and the majority of Infinite Power leave ANA without Shiwoo. Sena works hard on her song despite being ostracized in the company.

Hyeonwook gets Shiwoo to stay with ANA as a solo singer, and the company must work as a team to transform his image. Sena must re-work her lyrics to match the feelings of a man instead of a woman.

Sena is let down when her song isn't used for reasons beyond her control. As Shin Haeyoon notices Hyeonwook and Sena getting closer, she becomes increasingly jealous.

Shiwoo starts to develop feelings for Sena and Hyeonwook takes notice. Sena receives good news about her song.

Jaeyoung interferes with Shiwoo's solo stage. After their most recent event, Hyeonwook and Sena are unsure of how to act around each other.

Hyeonwook distances himself from Sena after she gets fired. Shiwoo hires Sena to work on a new song for him.

Hyeonwook decides to be honest with himself and starts dating Sena, but the truth about Sena's sister is still hidden from her.

As Shiwoo's song gains popularity, offers start rolling in for Sena as a songwriter. Hyeonwook is nervous as Jaeyoung starts mentioning Yoon Soeun to Sena.

Sena finally discovers the truth about her sister's past relationship with Hyeonwook, and distances herself from him.

With her emotions in disarray, Sena has trouble composing a new song. To make things worse, Shiwoo accidentally starts his own scandal.

The passing of a good friend brings Sena and Hyeonwook closer again, but Hyeonwook's father interferes when he finds out who Sena's older sister is.

Thanks to Sena, Hyeonwook can finally compose songs again, but Sena's next decision changes their relationship drastically.