Tae-Hyeong and Hyun-Jin sign a cohabitation agreement at home in Our Universe episode 3. Hyun-Jin reaches out her hand to Tae-Hyeong. He shakes hands with her. He wants to continue to use the room after he discovered that the room was very clean. But she stops him. He wonders if he needs to sleep in the master bedroom. She allows him to sleep in the room. But she doesn’t want him to touch anything in the room. He asks her to knock at the door when she visits him.
Hyun-Jin knocks at the door of Tae-Hyeong’s room. He opens the door. She asks him to promise her that he will only live for one month. She wonders how he will take care of Woo-Joo since he doesn’t have a job.
The next day, Tae-Hyeong goes to the company to take a month off. But the boss asks Tae-Hyeong to be a photographer. Tae-Hyeong goes to the motel to take photos. He runs into Mu-Saeng. Mu-Saeng is Amy Chu’s assistant. He guesses Tae-Hyeong is a photographer. He hands over his business card to him.
Tae-Hyeong returns home. He remembers Mu-Saeng told him that he wants to hire him for one day. Hyun-Jin walks into Tae-Hyeong’s room. She asks him to check Woo-Joo everyday and report it to her.
The next day, Hyun-Jin asks Tae-Hyeong to take care of Woo-Joo. Because she needs to go out. She claims that he needs to cooperate with her. Because she has a job. He reminds her that it will count as overtime pay. She asks him to move out if he’s not happy with it. He offers to build mutual trust. But she asks him to prove it with action. She goes out. He feeds Woo-Joo.
Hyun-Jin gets on a bus. She’s very happy. She arrives at the company BS Food. She joins the company. But she’s just a contract employee. Tae-Hyeong cleans the floor at home. He sees the note Hyun-Jin left. He learns that she wants to use picture book games to spark the baby’s creativity. He thinks it’s not a good idea. Because the baby is educated through audio-visual means. He remembers he needs to report it to her. So he takes a photo of the baby.
At BS Food, Hyun-Jin is taking class with other employees. She receives a photo of the baby from Tae-Hyeong. He claims that the baby’s creativity and language skills rapidly elevated like his aunt. She’s very happy. She eats with other colleagues. She receives a photo from him again. The baby is eating on his own. She’s writing the food evaluation form. The baby visits the cafe. He’s building muscle. Tae-Hyeong trains the baby what he shouldn’t do. The baby tries to follow Tae-Hyeong into the room. Tae-Hyeong stops the baby. Because he needs to take a break.
The new employee training has concluded. Tae-Hyeong takes bath in the bathroom. The water is cold suddenly. So he walks out of the bathroom. Hyun-Jin returns home. She sees Tae-Hyeong. She screams when she covers her eyes. She asks him what he’s doing. He explains it to her that he was attacked by cold water after the water heater was turned off.
Tae-Hyeong cannot fix the water heater. Hyun-Jin thinks the guy isn’t useful. He talks back that the house is in poor condition. She reveals her sister fixed the water heater before. She contacts the repairman. But he asks for one million won. Hyun-Jin blames Tae-Hyeong for not taking bath for Woo-Joo first. He asks her what she would do if the water turned cold. He lets her take care of it on her own. He walks away. She thinks he’s too heartless.
Tae-Hyeong and Hyun-Jin team up to take bath for the baby. Tae-Hyeong praises himself. Hyun-Jin complains it to him that she would get it done within thirty minutes if he caught the baby. He claims that he’s a volunteer. He reminds her that it’s midnight. He thinks she has no conscience. But she tells him that he’s too stingy.
The next day, Hyun-Jin is in the restroom at BS Food. Tae-Hyeong sends a message to her. He thinks she shouldn’t let others find out that she didn’t take a bath. She goes to the office. She puts the stuff on the desk. Gyu-Jung shows up. He learns that she prepared those things. He thinks she feels lonely as a contract employee. She denies it. She thinks she should have prepared those things on her own. He gives her the paper of the company structure. He asks her to check it. But she has checked it three times. He thinks she’s a model employee. He brings up that Tae-Hyeong called her wife in the lobby at the company.
Hyun-Jin and Se-Yeon watch the video together. Se-Yeon doesn’t expect that the person was Hyun-Jin. She finds out that the bell pepper guy’s face was captured very clearly. Fortunately, only Hyun-Jin’s back view was captured. Hyun-Jin gets angry when she looks at Tae-Hyeong. She wants to pop his dimples.
Tae-Hyeong plans to fix the water heater. He contacts his friend. He’s told that he needs tools. He visits his neighbor. He wants to borrow some tools from him. The neighbor likes Woo-Joo very much. He learns that the baby cannot take a bath because the water heater is broken. The neighbor volunteers to fix the water heater. He asks Tae-Hyeong about him and Hyun-Jin’s relationship. Tae-Hyeong says that they’re baby relationship since they they take care of baby together.
At BS Food, Hyun-Jin is in the elevator. She complains that she keeps getting into trouble. She returns to planning team. Gyu-Jung scolds her when he wants to know where she went. He reveals the team leader came. She sees Yoon-Sung. She remembers they took a walk in the wild. They tried to hold each other’s hands. She’s shocked after she recognized him. He walks to her. He introduces himself to her. She steals a glance at him when he works.
The neighbor ruins the water heater. He flees. Hyun-Jin is on the bus in the evening. He texts Tae-Hyeong. She apologizes to him for not going home on time. She complains that she wants to take a hot bath. Hyun-Jin is at home. She tries to open the water heater. But she fails. She brings up that she could open it at least yesterday. She questions Tae-Hyeong if he touched anything. He denies it. She looked into it. She found out that the landlord should be responsible for repairs. She thinks they didn’t make any mistake. She contacts the landlord. But the landlord doesn’t pick up her phone. Tae-Hyeong tells Hyun-Jin that the landlord is terrible. He thinks the guy intends to go missing. He sends a message to the landlord for her with a tone that he’s her husband. She gets angry. He volunteers to do something for her.
Hyun-Jin, Tae-Hyeong and Woo-Joo are in the Laundry Room. Tae-Hyeong complains it to Hyun-Jin that he keeps working overtime. She reminds him that her life is a mess because of him. She’s furious to show him the video that he calls her wife at her company. She wants to let Yoon-Sung see her perfect side. She confesses it to Tae-Hyeong that Yoon-Sung is her first love, and she likes the guy very much.
The next day, Hyun-Jin takes a cold bath because the water heater is broken. Tae-Hyeong reminds her that she will catch a cold. But she thinks the social life is very important. She asks him to make sure that Woo-Joo finishes all the food. He needs to send a photo to her.
Hyun-Jin is in her room. She opens a box. She smiles. She sees the group photo of her and Yoon-Sung. She’s shy. The next day, Hyun-Jin coughs. She intends to take a cold bath again. She goes to the company. She greets her colleagues. She overhears that Yoon-Sung will go on a business trip tomorrow. She thinks it’s fine that she doesn’t take a bath one day.
The next day, Hyun-Jin is going to go out. Tae-Hyeong notices that the girl’s face looks a little pale. He worries about her. She thinks she’s fine because she didn’t wash her head with the cold water. She goes to the office. She sees Yoon-Sung. The guy doesn’t go on a business trip.
Tae-Hyeong washes Woo-Joo’s clothes at home. He complains it to Woo-Joo that the water heater makes anything so hard. He learns that he and Woo-Joo need to take a bath today. He takes out Mu-Saeng’s business card from his pocket. He remembers what Mu-Saeng told him that his daily wage is one million won. He arranges his friends to take care of the baby.
Tae-Hyeong meets Mu-Saeng outside the studio. Mu-Saeng asks the guy to obey Amy Chu’s orders. Tae-Hyeong gets into the studio. He begins to work. Amy Chu shows up. She learns that he’s her new assistant. She doesn’t like him. She asks him to leave. He rejects it. Because he wants to get one million won today. The model throws a fit to Amy Chu. She complains it to her that she was labeled as a mistress, and she lost the advertising endorsement. She refuses to take photographs otherwise Amy Chu changes a style. Amy Chu tells the model that she’s not interested in her affair. She reminds her that she wanted her to show current her when she visited her. She claims that she’s going to change the way those guys look at her with her camera. She lets her make a choice.
The model stays in the studio. Amy Chu takes photos of the model. Tae-Hyeong moves the light forward. Amy Chu doesn’t understand why he did it. He points out that she wants a stronger sense of light-dark contrast. She learns that he made unauthorized adjustments without her instructions. He knows she doesn’t like others to mess around in her studio. But he only works for one day. So he doesn’t have to flatter her. He reminds her that she likes the distorted hues.
At BS Food, Yoon-Sung has a meeting with the planning team. He wants to expand into overseas markets. Hyun-Jin thinks it’s a chance. He notices that she coughs after the meeting. Tae-Hyeong goes to his friend’s place to pick up Woo-Joo. We are told that the guy wanted to work for Amy Chu.
Yoon-Sung and Hyun-Jin are off duty together. He asks her to take his car. The repairman fixes the water heater. Tae-Hyeong pays the repairman one million won. The baby messes up Tae-Hyeong’s room. Tae-Hyeong finds his camera. He remembers he tried to throw away the camera.
Yoon-Sung drives Hyun-Jin home. He wonders when she moved into the house. He mentions they hadn’t seen each other for a long time. He thinks it’s seven years after they parted ways. She doesn’t expect that she would encounter him in such a way. She mistook that he forgot her. She brings up that he didn’t greet her at the company. She wonders if she was sad. She denies it. He offers to get along well in the future. He smiles. He drives away. She complains that she lied to him. She thinks he’s not changed.
Yoon-Sung is on the way home. He remembers he tried to confess his feelings to her in the wild. But she told him that she needs to go to the school overseas. So they cannot see each other.
Hyun-Jin returns home. She finds out that the house is a mess. She learns that Tae-Hyeong went out and he arranged Woo-Joo. She brings up the contract that he promised to maintain the tidiness of the home. She thinks he should report it to her if he wants to take the baby to go out. He complains it to her that he did the thing that he doesn’t usually do for the home. He took camera after three years. He brings up that he had a condition that nobody shouldn’t get into his room. But the baby did it. He thinks he didn’t have an easy time because of her. But she tells him that he ruined her. She became a lobby girl and she couldn’t take a bath. He points out that he went to work. He thinks she’s dirty. She agrees with what he said that she’s dirty. She knows she’s terrible. He asks her to go to take a bath. She rejects it. Because she knows it’s very cold. He reveals he has let the repairman fix the water heater.
Hyun-Jin walks out of the bathroom after she took a bath. She joins Tae-Hyeong when he’s drinking. She thinks he should eat appetizers. She takes out a bottle of red wine. She confesses it to him that she wanted to drink. She was in a terrible mood because she lied. But she felt better after she took a hot bath. She wonders where he got the money. She knows he’s broke. He brags it to her that he used his daily wage to pay the repair costs. The next day, the two find out that they sleep together. They scream. But the baby is very happy.