Futuristic post-war Japan is divided into four military regions, each led by conflicting nations trying to gain complete control over the country. While the Boundary War—fought with the help of humanoid mecha weapons called AMAIM—has long been over, the rivalry between these factions is still ongoing, and, as a result, the Japanese are heavily oppressed. Amou Shiiba, a 16-year-old orphan boy who is secretly rebuilding an abandoned AMAIM named Kenbu, stumbles upon Gai, an autonomous AI in need of battery power. By choosing to help one another, Amou and Gai find themselves at the center of a disaster, and Amou is labeled a terrorist and cast out of society. Even so, Amou refuses to remain idle in the face of injustice, and he embarks on a long journey rife with struggle and companionship. His aim transitions from leading a peaceful life to liberating the Japanese people.

New entry in the Kyoukai Senki franchise.

Two years have passed since the EL-Divers incident, and the popularity of the game Gunpla Battle Nexus Online (GBN) has continued to skyrocket. With the addition of exciting new features such as missions and story events, the GBN experience is more immersive than ever before. Amidst the player base, a user known as Hiroto Kuga has been gaining notoriety for his top-notch skills. Through a series of coincidences, Hiroto meets three other players: the boastful Kazami Torimachi, the mysterious May, and the timid Parviz. Forming the "BUILD DiVERS," the unlikely group sets on a story mission rumored to carry bountiful in-game rewards. Together, the BUILD DiVERS must confront their own weaknesses as they join arms in a journey that may very well transcend the existence of GBN itself.

It's the highlight of GBN's anniversary event, the "Gunpla Battle One-Day Battle Royal"! Participants are selected from the Divers who played most passionately this season, and they're fighting in machines randomly assigned mainly from those Gunpla ranked highest by all Divers in the Great Gunpla Ballot! Now the final round is about to begin, with the tough fighters who've won their respective blocks! There, an unpredictable, super special, never-seen-before Gunpla dream battle will... START!!! (Source: AniDB)