Episode 4 of "Idol I" begins with a flashback of Se-na learning about Ra-ik’s relationship with Hye-ju from the news. Se-na is devastated to discover that her beloved idol is dating, and she mopes around for days. Eventually, when Ra-ik’s management denies the rumor, Se-na is relieved and returns to her normal self. In the present day, Se-na stands by Ra-ik as Hye-ju embraces him. She notices someone taking photographs of them and drives the person away so they can talk in private. As Se-na waits at the corner of the street, watching the former couple converse, Chung-jae arrives to see her.
When Chung-jae learns that Hye-ju is Ra-ik’s ex, he recalls how Se-na reacted to Ra-ik’s dating rumor all those years ago. Ra-ik confronts Hye-ju about showing up in his life again and tells her off. Hye-ju claims that on the night of Woo-seung’s murder, she saw Jae-hee outside Ra-ik’s apartment when he was supposed to be at the hospital with Young-bin.
Ra-ik returns to Se-na and takes Chung-jae’s bike to visit Jae-hee. He asks Se-na to drop Hye-ju home, but she is upset with Ra-ik for keeping the truth about his relationship from her. Meanwhile, Detective Yoo and Byung-kyun discuss Ra-ik’s involvement with Imhwa Group’s heir, Hye-ju. Se-na also asks Chung-jae to look for dashcam footage from the taxi that passed by Ra-ik and Hye-ju on the night of Woo-seung’s murder.**
Jae-hee tells Manager Han-gu and Young-bin that he plans to meet CEO Geum Bo-sang to have his contract terminated. He claims that he wants to protect his career from the scandal, but Young-bin feels betrayed. Ra-ik then shows up at the dorm and confronts Jae-hee. The two idols argue again, forcing Manager Han-gu to step in. Young-bin defends Jae-hee’s alibi, and the manager asks Ra-ik to leave.
At Cheon Un Law Firm, Se-na continues to dwell on Ra-ik’s relationship with Hye-ju and recalls how he looked sad and withdrawn even during public events. She concludes that Ra-ik was suffering through a breakup while being forced to perform and make public appearances. She eventually pulls herself together and tries to ignore her feelings about his dating life.
Ye-sol then shares with Se-na a news article involving Ra-ik and Hye-ju. Se-na decides to meet the reporter to get the article taken down. Ra-ik calls her, asking her to handle the situation since Hye-ju needs to be protected from public scrutiny. Ra-ik confronts the reporter, Baek, over publishing the article without Hye-ju’s consent. Baek recalls taking photos of Hye-ju with other male idols and calls her an opportunist, angering Ra-ik. As Ra-ik threatens him, Se-na arrives and intervenes. Since Hye-ju is not a public figure, the reporter can be sued for publishing private photos. She demands that the article be taken down and leaves with Ra-ik.
Outside, Se-na confronts Ra-ik about keeping things from her while she defends him in court. A flashback shows Ra-ik meeting Hye-ju after she pesters Woo-seung, while Jae-hee spots Ra-ik and Woo-seung arguing over her. In the present, Ra-ik tells Se-na that Hye-ju tried to get back together with him and claims that she later saw Jae-hee outside his apartment.
At the same time, Byung-kyun confronts fellow prosecutor and Hye-ju’s brother-in-law, Gi-wook, about setting him up on a blind date with her. He brings up Hye-ju’s relationship with Ra-ik and asks for her to be questioned. During the interrogation, Hye-ju claims she met Ra-ik as an old friend in the privacy of their car. She accuses Byung-kyun of targeting Ra-ik without properly checking his alibi and brings up Jae-hee being seen near Ra-ik’s house on the night of the murder.
That night, Young-bin confronts Jae-hee for lying about Ra-ik and Woo-seung’s fight and tells him to back off. Se-na later has an awkward moment when she finds Ra-ik changing his shirt. She then goes to Chung-jae’s house to think of ways to help Hye-ju and confides in him about how Ra-ik’s relationship has been troubling her and how he has been suffering internally for years.
Ra-ik looks around the house and finds old photos of Se-na from her childhood. Later, Se-na returns home to find Ra-ik asleep at the dining table and gets teary-eyed watching him sleep, thinking about everything he has silently endured.
The following morning, Ra-ik awakens to find breakfast left out for him. Chung-jae brings over Ra-ik’s skincare products and supplements that Se-na had asked him to drop off. As he savors the candy Se-na once gave him as a child, Chung-jae finds himself lost in thought about her.
Ra-ik meets Se-na at the prosecutor’s office, where they unexpectedly run into Byung-kyun. Se-na hands over taxi footage confirming Ra-ik and Hye-ju’s alibi and argues that Woo-seung was alive at the time of Ra-ik’s return. Byung-kyun alleges that Ra-ik conspired against Woo-seung, prompting Se-na to counter with evidence. Their argument escalates, and Byung-kyun fails to refute her claims. Se-na leaves the pretrial hearing after proving Hye-ju’s innocence.
Outside, Ra-ik gives Se-na a hug and thanks her. Byung-kyun then appears and calls her by the name he used to bully her with. Se-na asks Ra-ik to wait in the car while she speaks to the prosecutor. In private, Byung-kyun accuses her of being obsessed with defeating him. Se-na mockingly dismisses his victim complex and walks away.
On the drive home, Ra-ik’s jealousy flares up over Se-na’s connection with Byung-kyun and asks if he is her ex. She loses her composure, rants about him being her enemy, and suddenly loses control of the car, driving off the road.
