Crushology 101

When it comes to dating, Hee Jin cares about looks. Having high standards for men, however, good-looking guys have no interest in her. Therefore, she ignores her boyfriend, Bong Soo’s looks. Meanwhile, Bong Soo makes a big mistake and humiliates Hee Jin. Hee Jin was going to take a leave of absence, but she changed her mind immediately after bumping into a good-looking guy.

Hee Jin is determined to pay back her debt of 2,000 dollars. However, she lacks the means to do so and decides to work part-time at an exhibition. There, she meets another handsome guy. Hee Jin also decides to enter a strength contest to win a brand-new tablet and be freed from her debt and notetaking.

Ah Rang agrees to do the alumni interview as Hee Jin asked him to. Seeing Hee Jin getting closer with Ah Rang, without knowing, Jae Yeol is concerned about Hee Jin and tells Hee Jin that Ah Rang isn't a nice guy. Meanwhile, Ah Rang wants to see Hee Jin in private, and he invites her to his studio.

After checking the conversation between Ah Rang and Ji Young, Jae Yeol runs to Hee Jin, worrying that she would be fooled by bad guys again. However, Hee Jin thinks what Jae Yeol does is cross the line and doesn't listen to him. Out of concern, Jae Yeol asks Ji Won for help. Meanwhile, Hee Jin finally gets to see the real side of Ah Rang.

Hee Jin tells Jae Yeol what happened that night, thinking he would be embarrassed about it. However, Jae Yeol doesn’t get startled by it, and he confesses his feelings again. Hee Jin is still in doubt, but unexpected events make her think about him again. Meanwhile, Yeo Reum, who is a popular sports announcer, comes to school, and it seems like she and Jae Yeol have a history.

Hee Jin and her friends find out that Jae Yeol and Yeo Reum were a couple a few years ago. Hee Jin doesn’t show it to others, but she’s bothered by it. Jae Yeol tells Hee Jin that there’s nothing between him and Yeo Reum, and this makes Hee Jin relieved. Watching them, Ji Won gets confused about his feelings toward Hee Jin. Meanwhile, Yeo Reum comes to school to see Jae Yeol again.

Multiple misunderstandings build up between Hee Jin, Jae Yeol, and Ji Won, causing Hee Jin to believe that Jae Yeol still has feelings for his ex, Yeo Reum. Meanwhile, the campus bustles as the school festival approaches with the Confession Tree event, planned to be hosted by Yeo Reum.

Jae Yeol and Ji Won’s war of nerves escalates after the incident of the Confession Tree. While Jae Yeol is tormented between Hee Jin and Yeo Reum, he finds out about the truth behind his breakup with Yeo Reum. Hee Jin and Ji Won keep running into Jae Yeol and Yeo Reum, and they end up sharing a meal together at the same table

Just as Bani and Yeol find happiness, disaster strikes Bani's family finances and her crucial art project is jeopardized. Reeling from setbacks and leaning on Ji Won for support, she unknowingly fuels Yeol's suspicions. Their fairytale beginning crashes hard against grim reality.

While Jae Yeol’s suspicions grow, Hee Jin applies for a scholarship program in the US. Things become more uncomfortable with the realization that the two must stay apart if she is accepted. On top of that, Ji Won also decides to go to the US to stay with his parents and sister.

Hee Jin comes back to Korea after a year in the US. As she returns to school, she encounters Jae Yeol, her ex. Meanwhile, she also runs into Hyun Oh, her first crush from when she was little. As the three coincidentally keep bumping into each other, a whirlwind of emotions ensues.

Jae Yeol wants to tell Hee Jin how he feels about her, but Hee Jin ends up misunderstanding his true intention. Hyun Oh asks out Hee Jin, and it makes her even more confused. Meanwhile, Jae Yeol finds out that he lost the hard drive that has all the work of his commercial footage. Hee Jin ends up helping Jae Yeol find the hard drive, and Jae Yeol finds another chance to confess his feelings.