Plot

The timid, young Asuka is bullied by her classmates. When they embark on a class field trip to Korea, Asuka plans revenge by sending them a cursed phone message they can either pass on or die.

High school student Pam hangs herself at school due to severe bullying from her classmates, but she is saved and committed to a hospital in a state of coma. Her friend, Asuka Matsuda, who is also bullied, plans to take revenge against their classmates, all of whom have gone to Busan, South Korea on a field trip.

Using her computer, she clicks her class photo to place the cell phone curse. Her first victim is Azusa Kusunoki; Azusa receives a message accompanied by a photo showing her hanged. At Busan, Azusa is separated from her classmates in a busy marketplace and is killed when a noose drags and hangs her, with her spitting out a red candy afterwards. Teruya Mikami receives the message next, but now accompanied with the text "Death exempt by forwarding the message". He shrugs it off and goes to a restroom, but is killed when a loose telephone wire electrocutes him to death. More students start to receive the message, and in a panic, they start to forward it to their friends, saving them at the cost of their friends' lives.

Asuka's close friend, Emiri Kusama, whose boyfriend, Ahn Jin-woo, is deaf, calls Asuka to stop her, to no avail. They learn that the curse came from Mimiko Mizunuma, a girl who died from asthma. Emiri reveals to Jin-woo that PAM is a nickname for Asuka to denote her status in their class (a diminutive of "Spam"), exposing the current Asuka as her impostor. She also reveals that Asuka became the target of bullying after standing up for her, who was originally the one bullied first. With Jin-woo's advice, Emiri apologizes to Asuka, causing the real Asuka to awaken from her coma.

Realizing that the curse's source is Asuka's computer, Emiri and Jin-woo race to send mails to overload the computer's inbox, with help from their friends who spread the news through South Korea and Japan. While sending mails, Emiri's computer connects with Asuka's at the same time when Asuka comes back home. The two have a conversation, but when Emiri receives the cursed message, both are transported to different places in their school. Finding Asuka about to commit suicide with Mimiko, Emiri recalls their promise to visit the shore and offers herself to replace Asuka. Before Mimiko can do so, Asuka's computer is overloaded and the two are sent back to their previous places.

While parting ways with Emiri, Jin-woo secretly snatches her phone (which still has the curse), and forwards the message to himself. Emiri realizing what he had done, tries to save him, but he had locked the door from the outside as a result, Emiri watches in shock as he is slowly killed. Some time later, Asuka and Emiri, the latter having lost her ability to speak and walk due to all the events that occurred, visit the shore as promised. (Courtesy of Wikipedia)