She’s on Duty

An orphan who becomes a police detective and goes undercover in a high school to protect Seung-hee and gather intel on her father. She is initially reluctant but grows into a determined, capable officer under pressure. Her feelings for No-young complicate her sense of duty, creating a romantic conflict amid the case. A personal tragedy—the stabbing of her uncle—drives her deeper into the investigation and tests her resolve.

A handsome classmate and next-door neighbor who is secretly an undercover agent. He stays close to Jae-in for information but gradually reveals genuine care and loyalty. His dual identity creates tension as he assists her while concealing his true mission. Their bond culminates in a kiss during their undercover life.

A notorious gangster boss whose empire drives much of the film's conflict. He wields power and a vast network to evade law enforcement, prompting dangerous gambits and rival schemes. His enemies seek to use Seung-hee as leverage, elevating the stakes for everyone involved.

Cha Young-jae's daughter and a high school student who becomes the focal point of rival schemes. She seeks safety and friendship, forming a bond with Jae-in that complicates her father's criminal world. Her loyalty and vulnerability highlight the consequences of crime on the next generation.

A newly arrived Class Teacher who appears supportive to Jae-in and Seung-hee, but is secretly an undercover operative. He becomes a pivotal ally, though his loyalties prove murky and eventually reveal a betrayal. His actions turn the investigation on a dangerous trajectory and heighten tension.

A seasoned police detective who coordinates the undercover operation and guides Jae-in through the case. He provides experience and leadership, but the pressure of the mission tests his own boundaries. His involvement sharpens the tension between duty and personal risk in pursuing Cha Young-jae.