A Blood Pledge

Four girls vow to die together that night on the school rooftop. Their pact tightens into a chilling resolve as they cling to the idea that their fates are linked. Soon after, Eun-Joo jumps from the roof and dies, an act witnessed by her sister and the others.

The following day, So-Hee admits in the school office that she was on the roof with Eun-Joo. Her admission unsettles the others and deepens the school's unease. Rumors begin to spread about who knew what happened that night.

Whispers accuse So-Hee of causing Eun-Joo's death, and friendships begin to fracture under the strain. Jeong-Eun confronts So-Hee, who maintains that she doesn't know what happened. The group grows suspicious, and secrets from the past resurface.

That evening, Eun-Young is beaten by her father for having low grades, revealing the cruel pressure she endures beyond school walls. The following day she begs Yoo-Jin to let her sleep at her home, seeking safety among friends. The violence outside school adds to the sense that their world is unstable.

So-Hee is haunted by memories of when she was friends with Eun-Joo, and she feels the weight of her past actions. Joo-Yeon accuses So-Hee of pushing Eun-Joo away, insisting she is to blame. Eun-Joo's past actions include killing Joo-Yeong, a revelation that intensifies the group's tension.

Eun-Young begins seeing Eun-Joo's ghost repeatedly, terrified by her presence. At the same time, So-Hee discovers a dismembered body in a classroom locker, possibly Joo-Yeon's, shocking the group. The two clues deepen the sense that the school hides deadly secrets.

Eun-Young tells Yoo-Jin that Eun-Joo promised they would not be harmed if they confessed honestly. The revelation binds the four girls with a fragile code of truth, yet suspicion lingers. The confession promise becomes a catalyst for their next actions.

Later, Yoo-Jin and So-Hee see Eun-Young on the roof and beg her not to jump. She refuses, declaring she no longer fears returning to her abusive home. Moments later she actually jumps, expressing relief that she won't have to face her past again.

So-Hee goes into a church to apologize for her role in the events, followed by Yoo-Jin. A flashback shows So-Hee with Ki-Ho, and the way Yoo-Jin used to date Ki-Ho, revealing how friendships fractured. In the present, the group’s tensions intensify as they confront painful truths.

In the present, Yoo-Jin claims she would kill herself if she can't beat So-Hee at school, while Eun-Young recalls a recent attempt to hurt herself because of her father. So-Hee finally confesses she is pregnant, adding another layer of pressure to the girls’ competing lives. Ki-Ho’s history resurfaces as betrayals and loyalties are tested.

Believing they need to outdo each other, the girls decide to pretend to jump and test their limits. Yoo-Jin ties a microphone around So-Hee's neck as part of the ruse, hoping to provoke a reaction. Eun-Joo storms in and strangles Yoo-Jin, showing that the plan has spiraled beyond their control.

On the rooftop, the four meet and hold hands as they prepare for another pretend jump. Before the jump, Eun-Young and Yoo-Jin step back; Eun-Joo hurls herself to her death before anyone can stop her. Jeong-Eun grabs So-Hee's hand and Nae? So-Hee is urged to stay and become the caregiver for Jeong-Eun.

So-Hee decides to keep the baby and moves forward while Ki-Ho has moved on. They step into an elevator, and as the doors close, the face of one of the girls seems to morph into Eun-Joo’s, leaving a haunting final image. The closing scene suggests the past may never truly be behind them.