In a flashback a girl called Himiko explains to her friend Miho that she was invited to play Btooom! with Team Sakamoto. Back in the present Himiko discovers that she had been parachuted onto the island with limited rations and a pouch full of bombs as well as her stun gun. In another flashback, Himiko and her friends discuss a strange chain letter that had been making the rounds on the internet that claims to reward anyone with 100,000 yen in exchange for allowing the "disappearance" of a named person of the email receiver's choosing. Back on the island Himiko awakens to find herself amid three men, Mitsuo Akechi, Isamu Kondō and Masashi Miyamoto. They decide to team up but when Isamu gets into constant disputes with Masashi, Masashi slits his throat; killing him. Mitsuo and Himiko then run away while Masashi is asleep but he quickly catches up to them only to retreat when Mitsuo uses his bombs. In another flashback, Himiko and her friends, Yuki, Arisa and Miho are invited by an upperclassman, Yoshioka to an apartment. When Himiko shows up late she discovers her friends were drugged and raped by Yoshioka and his band. They attempt to rape Himiko however she escapes and alerts the authorities. Afterwards, her best friend, Miho ends their friendship and blames her for the crime. In the present, Mitsuo becomes delusional and Himiko stuns him and runs away but he finds and sexually assaults her. However, Himiko activates one of her timer-BIMs, deciding to kill them both but when Mitsuo runs she throws the bomb after him which explodes and kills him. Himiko then deems that everyone on the island is her enemy, especially the men. At this point, when Himiko is refreshing herself at the river, she is discovered by Ryouta.