Now that he and Song-yi are officially dating, Do-hyun wants to let Tae-oh know about it but Song-yi wants to date secretly for a while. The next day at the university, Song-yi gives Do-hyun a tour of her department while Tae-oh takes Se-hyeon shopping. At the meeting for their college project, Se-hyeon turns up late with Tae-oh beside her. Song-yi is shocked to see the two together and Tae-oh feels awkward about Song-yi finding out.
Song-yi calls Se-hyeon out for not putting work into the group project. Instead of admitting her mistake, Se-hyeon derails the conversation to Tae-oh, leaving Song-yi upset. At home, Song-yi confronts Tae-oh and he admits that he felt weird telling her that his girlfriend is now living at her old house. Song-yi tries to be mature about the whole thing but quickly gets annoyed at seeing Tae-oh doing Se-hyeon’s homework.
Hoon has trouble following the choreography of his musical and is brushed off when he asks for help since he’s just an understudy. On his way home, he bumps into Ga-rin who is coming back from her part-time job and because he now knows about her chaebol identity, he treats her unusually respectfully. When Tae-oh gets annoyed at Hoon for wearing his clothes without asking, Hoon stares longingly at the reward amount on Ga-rin’s missing poster, grumbling about being poor.
Song-yi asks Do-hyun to accompany her on a field trip and he enthusiastically agrees, assuming that it’ll be an overnight trip. He makes a disappointed face when Song-yi tells him she’s planning to return the same day and she calls him adorable.
Tae-oh asks Song-yi to move to the attic because it looks like it might rain and she finally tells him that she’s dating. He presses her for details about the guy, unable to believe she actually has a boyfriend now and has to convince himself not to worry about Song-yi’s love life.
Song-yi enlists all the housemates to help her pick a dress for a date but doesn’t tell them whom she’s dating. Hoon suggests a lovely pink dress but Tae-oh shoots it down, picking out T-shirts with rock bands on them and annoying everyone.
Song-yi is running late for her tuition classes and Tae-oh refuses to drop her off because he has a date. On his way out, Tae-oh notices Song-yi’s worn out purse and shoes.
Do-hyun turns up with his delivery scooter and offers to drop Song-yi to Tae-oh’s parents’ house. Song-yi holds Do-hyun tight and the two smile throughout the ride. They bump into Tae-oh at a red light, who finds it strange that Do-hyun and Song-yi are close.
Tae-oh notices a pretty pair of shoes and a matching purse in a shop and buys them for Song-yi. She’s pleased to discover her gifts and shows up to her date looking so pretty that Do-hyun is unable to take his eyes off her.
The lovebirds have a ridiculous amount of fun window-shopping, trying different foods, and taking a doll-painting class together. Tae-oh and Se-hyeon, meanwhile, have their date at a park. They talk about the videos Tae-oh’s mom took of him as a kid and Se-hyeon suggests making a film with them. Tae-oh reveals that his mom passed away but promises to think about the idea. He goes home and watches the videos, calling a toddler Song-yi cute when she makes an appearance. Song-yi drops Do-hyun at his part-time job and he’s apologetic that he can’t walk her back home.
Tae-oh realizes that it’s raining and wonders where Song-yi is. She gets stuck in the rain and when a worried Do-hyun calls her, she lies that she’s almost home. Not wanting to ruin the shoes Tae-oh got for her, she puts them in a plastic bag and runs home barefoot. Tae-oh sets out to look for Song-yi with an umbrella. He finds her soaked and barefoot with a cut on her feet and gets angry. She reassures him that she’s fine, but he asks her to put on his shoes and they rush back home. Furious that her boyfriend didn’t drop her home, Tae-oh bandages Song-yi’s foot and asks why she didn’t just call him when she got stuck. Song-yi replies that she doesn’t want to bother him for small things now that she has a boyfriend.
The thunder is loud that night and Tae-oh guesses that Song-yi would be scared sleeping alone in the attic. He calls her, but before he can ask her to come down, Hoon and Ga-rin burst into his room scared out of their minds. The group spends the night watching Running Man. Tae-oh looks over at Song-yi laughing and thinks about how they can’t be close like before now that they’re both dating different people. He silently wishes for the line between them to not get any wider.