Sakamoto Ryota is an unemployed 22 year old who lives with his mother and spends his days doing nothing but playing video games. In the real world, there may be nothing special about him, but online, he's one of the world's top players of the combat game called Btooom. One day, he awakes on what appears to be a tropical island, though he has no memory of how he got there or why. While exploring the island, Ryota runs into a mysterious being who attacks him by throwing a strange looking bomb at him. Ryota then realizes that both his life is in danger, and that he has somehow become trapped in a real-life version of his favorite game. Ryota and the other "players" must now survive through the nightmare to figure out the reason why they ended up in the game in the first place.
The Empire of Britannia has invaded Japan using giant robot weapons called Knightmare Frames. Japan is now referred to as Area 11, and its people the 11's. A Britannian who was living in Japan at the time, Lelouch, vowed to his Japanese friend Suzaku that he'd destroy Britannia. Years later, Lelouch is in high school, but regularly skips out of school to go play chess and gamble on himself. One day, he stumbles on terrorists 11's who've stolen a military secret and is caught by a member of the Britannian task force sent after them, who is Suzaku. As the rest of the squad arrives, Suzaku is shot for disobeying orders, while the military secret, a young girl, gives Lelouch the power of Geass, which makes anyone obey any order. While Suzaku is secretly made the pilot of Britannia's brand new prototype Knightmare, Lancelot, Lelouch becomes the masked Zero to lead the rebellion to destroy Britannia once and for all.
Sotobamura is a small village with around 1300 residents; so small the village isn't even connected to a single highway. An isolated village in which old customs, such as the burial of the dead, are still practiced. One day, the bodies of three people are found dead. Although Ozaki Toshio, the village's lone doctor, feels uncertain, he treats the deaths as a normal occurrence. However, in the days following, the villagers start to die one after the other.
Enter Sentan, a lush, tranquil island encased in war between the military and those with Hiruko, known as X'amd. On one of these warlike days, Akiyuki Takehara heads off to school and gets caught in a raid by the creatures. Through a series of events he is transformed into a X'amd, and with the help of a Tessikan woman Nakiami along with his highschool friend Haru, Akiyuki is forced to learn to live with the Hiruko or faces the danger of losing his self-control and turn to stone.