START.Ryōta Sakamoto, an unemployed 22-year-old, is an elite Japanese player of Btooom!, an MMO which sold almost three million copies worldwide, with his team ranked as tenth in the world. In the present, an amnesiac Ryōta awakens in a parachute harness on a tropical island, only equipped with his bag containing a few necessities, a pouch full of countdown bomb-like weapons called Timer BIMs and a strange bead-like chip embedded on his left hand. Ryōta vaguely recalls a dispute he had with his mother Yukie Sakamoto, who wanted him to get a job rather than playing video games at home all day, but he harshly stated that he was pursuing a job at the video game company. After he visited a convenience store to revoke a job application Yukie turned in for him, he is met by two men, at which point his memory dissolves. At night on the beach, he is pursued by someone named Yoshiaki Imagawa, who attacks him with Cracker BIMs. Failing to reason with Yoshiaki, Ryōta is forced to evade behind the bushes, realizing that he is forced to play Btooom! for real. When Yoshiaki corners him near a cliff, Ryōta then sets a trap by leaving a Timer BIM on the cliff and jumping into the ocean, which kills his assailant unawares. Ryōta later dreams of yet another fight with Yukie about job hunting. He then stumbles through the jungle near a river, where a girl is seen refreshing herself.