Episode 5 of "Who Is She" kicks off in a dimly lit bar, where the enigmatic taxi driver, against the haunting melody of "Don't Turn Back," steadfastly refuses an elderly patron's request for a second chance. Transitioning to the present, Oh Du-ri, formerly Mal-soon, encounters a woman presumed to be the authentic Emily. Escorting her outside for a private chat, Du-ri's astonishment deepens upon discovering that this stranger is her very own twin sister. Just when the veil of secrecy is about to be lifted, the taxi driver interrupts, sternly reminding Emily of her vow of silence. In a whirlwind of confusion, Emily bolts, leaving Du-ri utterly perplexed.
Through Emily's hush-hush exchange with the taxi driver, a revelation unfolds: she is among those who have been granted a second youth. Meanwhile, Du-ri engages in a forceful negotiation with Daniel, securing a ten-day stay at her family's abode. Elsewhere, Ha-na's heart sinks as her grandmother fails to recognize her, sparking concerns of dementia among both Ha-na and Mal-soon's kin.
Arriving tardily to practice, Du-ri faces a harsh penalty: exclusion from the group until their debut. Shortly thereafter, Ae-sim treats the debutantes and their staff to a dinner that quickly turns sour as Du-ri deliberately stirs up trouble, her actions fueled by a painful memory. A flashback unearths the betrayal: Ae-sim had debuted with one of Mal-soon's compositions, a trust shattered when Mal-soon uncovered the deceit through a chance encounter with an acquaintance.
Excluded from official training sessions, Du-ri resolves to hone her skills in solitude. Meanwhile, Daniel stumbles upon evidence suggesting an intrusion at his residence, coinciding with yet another chilling message from his stalker. The following day, whispers about Mal-soon spread through the neighborhood and eventually reach her purported twin sister's ears, who listens with rapt attention. Pretending to have suffered memory loss due to an accident, the sister approaches a kindred spirit aligned with Mal-soon and is intimately recounted the latter's life narrative.
Elsewhere, a malicious debutant within the team orchestrates another obstacle for Du-ri, ensuring her tardiness for a crucial interim assessment. This same individual also surreptitiously records a video featuring Du-ri and Mr. Park. During the gathering, it transpires that Mal-soon had a sibling named Kkeut-soon, who departed for America as a child and subsequently severed all ties with Mal-soon.
True to prediction, Du-ri arrives late for her interim evaluation. Simultaneously, Daniel receives from Ae-sim a damning video clip of Du-ri and Mr. Park. Eavesdropping on Du-ri's conversation with Mr. Park about withdrawing Mal-soon's funds, Daniel jumps to the conclusion that she is entangled in a scandalous affair and promptly terminates her membership in the group.
