30, но 17

17-year-old violinist Woo Seo Ri becomes comatose after a major bus crash. Gong Woo Jin, a 17-year-old boy who likes her, witnesses the whole thing. 13 years later, at age 30, Seo Ri wakes up.

Seo Ri wakes up from her coma and realizes she is 30; Woo Jin's sister calls him back to Seoul.

Seo Ri learns that her aunt and uncle have moved.

Woo Jin, Chan, and Jennifer all hear something during the night. They go the first floor and are shocked to see something coming out of a cabinet. Seo Ri stays the night at Woo Jin's place and reveals how this house became as it is now.

Hyung Tae is eager to find Seo Ri and looks everywhere. Seo Ri finds out that the hospital is searching for her, yet decides not to return. Seo Ri realizes that Woo Jin used to go to school in Germany which made her curious about Woo Jin.

Seo Ri fails to make the cut for the orchestra, and Chan helps to comfort her feelings. While eating tteokbokki together, Seo Ri receives good news from the violin academy that she can perform for 2 to 3 weeks as a substitute.

Seo Ri sees a man who she thinks is her uncle while heading somewhere in a car. When she tries to runs to him while the car is still moving, Woo Jin encounters flashbacks of a bad memory and grabs Seo Ri to stop her from running.

Once Seo Ri realizes that she may have confused some other man as her uncle, Seo Ri feels regretful for talking so cruelly toward Woo Jin and chooses to apologize to him.

Woo Jin sees Seo Ri going into a bar while he is having a meeting with his clients. He follows Seo Ri and shouts her name loudly to find her, but soon gets dragged out by the bouncer.

While both Woo Jin and Chan have feelings for Seo Ri, each have very different approaches toward Seo Ri.

Seo Ri joins Hee Su's team to help her organize a music festival. However, Woo Jin feels uncomfortable with the situation and confronts Hee Su about the matter.

Seo Ri gets drunk during the team dinner, and accidently enters Woo Jin's room which brings a very awkward situation the next morning. Woo Jin tries to avoid Seo Ri to hide his feelings, but it get harder and harder.

Woo Jin sees his doctor and confesses that Seo Ri made him change to be a different person from what he used to be. Meanwhile, Chan decides to express his feelings towards Seo Ri after winning at the national competition.

Woo Jin gets drunk while he was trying to protect Seo Ri from Mr. Kang at the bar. Afterwards, Woo jin's behavior makes Seo Ri question the reason behind it.

Seo Ri is looking for a place to stay and Hyun’s cousin’s place becomes her favorite option as everything is free to use there. Chan is crushed to hear that she will move out since he has plans to admit his feelings for her.

Woo Jin takes Seo Ri to the ocean to cheer her up; Seo Ri shares her perspective with Woo Jin, who feels sorry for how he treated her.

When Chan's mom visits Woo Jin's place, they decide to lie and tell her that Seo Ri is their housekeeper to avoid any drama. However, Seo Ri feels uncomfortable about lying and tries not to be seen by Chan's mom.

Woo Jin convinces his father not to sell the house as he is planning to stay there more often without going abroad for months. In the meantime, Seo Ri and Hee Su get lost on an island as they cannot sail back home.

While Seo Ri and Woo Jin spend some time together at an empty house, Deok Su calls Woo Jin telling him that Chan has fainted. Woo Jin leaves the place immediately to see Chan which makes Seo Ri concerned.

Woo Jin feels uncomfortable as one of female employee tries to set a blind date up with Seo Ri and her son, so Woo Jin gets in the way to stop it.

While Woo Jin visits his therapist and tells him that he doesn't want to hide emotions from others just because he feels guilty about an incident that happened in the past.

Woo Jin accidentally overhears Byun's conversation with the reporter regarding spicing up the story about Seo Ri, so that people want to watch the pitiful girl.

After the motive behind the music festival is revealed, Woo Jin expresses that he doesn't want to see the woman he likes hurt. However, Seo Ri is persistent about performing and encounters a difficult time accepting the situation.

Shim tries to keep a jealous Tae Rin focused on her music; Seo Ri apologizes to Tae Rin for her shifting attitude about the performance.

Woo Jin and Seo Ri confess their feelings for each other and share their first kiss. Meanwhile, Hee Su becomes a full-time employee and shares her enjoyment with everyone.

When Seo Ri's aunt finds out Seo Ri's phone number, she tries to find out more by calling the hospital but fails to gather any information.

Woo Jin finds out that Seo Ri is the same person he once loved and emotions erupt while thanking her for being alive. Meanwhile, Chan is shocked after the nurse addresses Woo Jin as Seo Ri's boyfriend and denies to admit it.

When Seo Ri finds a drawing in the storage, she tries to seek Woo Jin as she realizes the person in the drawing is herself. However, Woo Jin is gone and waiting to get on the plane at the airport.

Finally Woo Jin confesses everything about the car accident to Seo Ri, saying it's all his fault. Seo Ri also confesses to Woo Jin that she had a crush on Woo Jin and liked him first.

Chan explains that he likes her more than as a friend, but also tells her that his feeling are all in the past. Later, Woo Jin informs Seo Ri that it was not her aunt and uncle who paid for her hospital bills.

Seo Ri's aunt decides to meet Seo Ri after listening to Woo Jin's message. Seo Ri's aunt can only apologize in tears when she finally meets Seo Ri. Later, Seo Ri finds out what her uncle did to protect Seo Ri's house from bankruptcy.