Episode 5 of Romance in the House opens with a flashback to Moo-jin and Ae-yeon's wedding day, where they exchange vows of eternal love. This serves as a stark contrast to the present-day tensions between them. In the present, Jeong-in, a woman with whom Moo-jin had a past relationship in Thailand, is drunk and calls out for him. She reveals that he had given her his entire fortune and that she had lost their child. Moo-jin remains silent and walks away.
Back at the villa, Ae-yeon advises Mi-rae to avoid petty competition with Moo-jin. Mi-rae, however, takes offense and leaves for work. In the elevator, she encounters Tae-pyeong and, for the first time, they have a meaningful conversation. This interaction sparks feelings for both of them.
Moo-jin tries to reconcile with Ae-yeon, professing his love for her. However, she is adamant about moving on and believes that their relationship is in the past. She tells him that there is no place for him in their lives and encourages him to find someone new.
While Moo-jin struggles to accept Ae-yeon's decision, Mi-rae and Ae-yeon have a heart-to-heart conversation about their relationships. Ae-yeon offers Mi-rae words of encouragement and support. Meanwhile, the neighbors gossip about Ae-yeon's recent behavior, speculating that she might be experiencing a midlife crisis.
Jeong-in, feeling guilty about her past with Moo-jin, reveals to Ae-yeon that she has a picture of her and Moo-jin together from Thailand. This shocking revelation leaves Ae-yeon in disbelief and denial.
At work, J-Plus is facing a crisis as a major supplier has decided to discontinue their business relationship. Mi-rae and Tae-pyeong must work together to secure a new deal. Despite facing challenges, Mi-rae's persistence and Tae-pyeong's connections eventually lead to a successful negotiation.
Moo-jin, struggling with his own personal issues, seeks solace at the beach. He encounters Tae-pyeong and Mi-rae, and finally reveals the truth about his past relationship with Jeong-in. He apologizes for his actions and expresses his desire to be a better father to Mi-rae.
However, Mi-rae is disappointed with Moo-jin's decision to leave. She believes that he needs to take responsibility for his actions and be a present father. Moo-jin, feeling guilty, agrees to stay and support his family.
As the episode concludes, Ae-yeon confronts Moo-jin about his past with Jeong-in. She questions whether he is the father of Jeong-in's child. Moo-jin, unable to reveal the truth, remains silent as Ae-yeon becomes increasingly upset.