The saga of the Knight Sabers continues as the group tries to find out who or what is behind the recent string of robberies, murders, and Boomer malfunctions which are somehow related to the creation of an advanced artificial intelligence. Furthermore, it seems that the Knight Sabers may be breaking up. (Source: ANN)

Five years ago, gravity-defying bubbles with mysterious powers rained down upon the earth. After a huge explosion of uncertain origin, Tokyo became ground zero, with the city being enclosed in a gigantic bubble. As a result of this Bubble Fall phenomenon, the metropolis that was once the capital of Japan drowned in a gravity-bending sea; the government declared it a prohibited zone, and the residents abandoned it. Children orphaned by the Bubble Fall now squat illegally in Tokyo, partaking in dangerous parkour team battles across the city's dilapidated buildings. Hibiki—a talented ace in these games with the ability to jump between bubbles—claims he can hear sounds from the Tokyo Tower. Determined to uncover its mysteries, he sets off toward the source, but he falls into the waters below. A strange girl, whom he later nicknames Uta, saves him. But little does Hibiki know that Uta's appearance in his life will reveal the secrets behind the disastrous event that changed their world forever.

Teppei is going to visit his older brother Kotaro Takamiya during a scientific conference after training with a mysterious woman named Karen for the past 11 years. However his plans for a family reunion become stalled when a woman named Aramis kills everyone in the conference to kidnap Kotaro. Teppei on the way to save his brother encounters a broken mechanical horse called B't X who revives thanks to Teppei's blood and is now his aide to save his brother from the mysterious Machine Empire.

Ryouta Sakamoto is unemployed and lives with his mother, his only real achievement being that he is Japan's top player of the popular online video game Btooom! However, his peaceful life is about to change when he finds himself stranded on an island in the middle of nowhere, with a small green crystal embedded in his left hand and no memory of how he got there. To his shock, someone has decided to recreate the game he is so fond of in real life, with the stakes being life or death. Armed with a bag full of unique bombs known as BIM, the players are tasked with killing seven of their fellow participants and taking their green crystals in order to return home. Initially condemning any form of violence, Ryouta is forced to fight when he realizes that many of the other players are not as welcoming as they may seem. Teaming up with Himiko, a fellow Btooom! player, they attempt to get off of the island together, coming closer and closer to the truth behind this contest of death.