During a field trip, Nanahara’s class is abducted and forced to participate in the Battle Royale program. In order to curb juvenile delinquency, the government has taken the drastic step of randomly selecting one class per year and force them into a brutal contest where only one student is allowed to survive. During their briefing, Nanahara’s friend Kuninobu is mercilessly killed as an example to the other students. Nanahara pairs with Nakagawa, Kuninobu’s old crush, and promises to protect her for Kuninobu’s sake. The students are armed and sent out into the wilderness on a deserted island, and the violence begins immediately.

Nanahara and Nakagawa befriend Kawada, a transfer student who was brought in to make the games more “interesting.” Kawada reveals that he has played in the games before, and was forced to kill his own girlfriend in order to survive to the end. He has “volunteered” to be reinserted into the games so that he can get his revenge on the system. Another transfer student, Kiriyama, is a psychopath who remorselessly guns down his fellow students for his own amusement. Kiriyama attacks Nanahara’s party, and Nanahara is separated from Kawada and Nakagawa. When he recovers he finds he is being held in a lighthouse occupied by several girl students. Nanahara’s presence causes the uneasy truce the girls’ formed to disintegrate, and more bloodshed ensues. Nanahara escapes and reunites with Kawada and Nakagawa. Kiriyama whittles down the players until only he, Nanahara’s group and another group led by Mimura are left. Mimura’s group has been tirelessly working with old computer parts found in an abandoned warehouse to try and sabotage the control center on the island so they can escape the games. They’ve also rigged a truck with a bomb to destroy the control center with. Kiriyama appears and interferes, forcing Mimura to detonate the bomb early in an attempt to kill Kiriyama. Mimura’s group dies, but Kiriyama somehow survives, only to be taken down in a firefight with Kawada.

Kawada stages the killing of Nanahara and Nakagawa so that he will be taken into the control center by the game runner, the class’ teacher Kitano. Kitano suspects Kawada of cheating, and reveals Kawada’s trick of turning off the tracking bracelets used in the game. Nanahara and Nakagawa appear and confront Kitano, who reveals that he sought to have Nakagawa win, because she was the only student who showed kindness to him as a teacher. Nanahara kills Kitano, and escapes the island with Nakagawa and Kawada. Kawada dies from his injuries during the voyage. Nanahara and Nakagawa are labeled fugitives from justice by the Japanese government and go on the run, attempting to flee the country.