As Jung-un delves deeper into the investigation, she discovers that the four girls had made a blood pact to commit suicide together as a way to escape their troubles and pain. Unjoo, who was always the outsider of the group, had been manipulated and bullied by the other girls, especially Soy, who harbored deep-seated jealousy towards Unjoo.
As Jung-un uncovers more about the events leading up to her sister's death, she realizes that there were dark secrets and betrayals among the friends. Eun-young had been hiding a traumatic experience from her past, while Eugene had been struggling with her own mental health issues. The dynamics of the group start to unravel, leading to shocking revelations about the true nature of their friendship.
As Jung-un gets closer to the truth, she becomes a target for the remaining girls, who will go to desperate lengths to protect their own secrets. In the end, Jung-un must confront the painful reality of her sister's death and the toxic relationships that led to it. Ultimately, she must find a way to move on from the tragedy and find closure for herself and her family.
