As Minjae seeks love, an unexpected incident reunites him with Youjin, a stranger he met before.

Youjin wants to go to grad school and asks Minjae for help. Will she make it into the robotics lab?

Feeling out of place on her first day, Youjin clashes with Sejin and finally snaps at Minjae.

As rumors spread that Minjae was seen with a mysterious woman, a jealous Youjin makes a bold move.

On a rainy night, Minjae can no longer ignore Youjin's bold feelings or his own.

Minjae and Youjin start a secret romance. From day one, the gap between them only grows.

Could this be Sejin's first love? Too bad his crush is Subin, the best friend of Youjin, his rival. When Minjae suggests they set the two up, Youjin feels slighted by the attention he gives Sejin. Her lighthearted prank to test Minjae's love ends up triggering his old insecurities. Meanwhile, bummed by an awkward first meeting with Subin, Sejin stumbles upon yet another unexpected scene.

When Youseong finds out about Youjin and Minjae, he opposes their relationship. But this time, Minjae refuses to back down, confronting Youseong and declaring that he will not give up on Youjin. Meanwhile, Sejin discovers their secret and challenges Youjin to a bet: the loser must leave the lab. If Minjae finds out, it is game over. A dangerous showdown between Youjin and Sejin begins.

Youjin grows increasingly close to Professor Jihoon. He shares that he met Minjae in the US and gives her Minjae's new contact information. But Youjin brushes it off, insisting that their love is over. Meanwhile, Youseong happens to get in touch with Minjae and secretly investigates the couple's past without Youjin's knowledge. What could have happened between two people who were once so deeply in love?