After a horrific alchemy experiment goes wrong in the Elric household, brothers Edward and Alphonse are left in a catastrophic new reality. Ignoring the alchemical principle banning human transmutation, the boys attempted to bring their recently deceased mother back to life. Instead, they suffered brutal personal loss: Alphonse's body disintegrated while Edward lost a leg and then sacrificed an arm to keep Alphonse's soul in the physical realm by binding it to a hulking suit of armor. The brothers are rescued by their neighbor Pinako Rockbell and her granddaughter Winry. Known as a bio-mechanical engineering prodigy, Winry creates prosthetic limbs for Edward by utilizing automail, a tough, versatile metal used in robots and combat armor. After years of training, the Elric brothers set off on a quest to restore their bodies by locating the Philosopher's Stone—a powerful gem that allows an alchemist to defy the traditional laws of Equivalent Exchange. As Edward becomes an infamous alchemist and gains the nickname Fullmetal, the boys' journey embroils them in a growing conspiracy that threatens the fate of the world.

In the year 2010, the Holy Empire of Britannia is establishing itself as a dominant military nation, starting with the conquest of Japan. Renamed to Area 11 after its swift defeat, Japan has seen significant resistance against these tyrants in an attempt to regain independence. Lelouch Lamperouge, a Britannian student, unfortunately finds himself caught in a crossfire between the Britannian and the Area 11 rebel armed forces. He is able to escape, however, thanks to the timely appearance of a mysterious girl named C.C., who bestows upon him Geass, the Power of Kings. Realizing the vast potential of his newfound power of absolute obedience, Lelouch embarks upon a perilous journey as the masked vigilante known as Zero, leading a merciless onslaught against Britannia in order to get revenge once and for all.

Surrounded by a forest and a gated entrance, the Grace Field House is inhabited by orphans happily living together as one big family, looked after by their Mama, Isabella. Although they are required to take tests daily, the children are free to spend their time as they see fit, usually playing outside, as long as they do not venture too far from the orphanage—a rule they are expected to follow no matter what. However, all good times must come to an end, as every few months, a child is adopted and sent to live with their new family, never to be heard from again. However, the three oldest siblings have their suspicions about what is actually happening at the orphanage, and they are about to discover the cruel fate that awaits the children living at Grace Field, including the twisted nature of their beloved Mama.

Yukiteru Amano is a shy middle schooler who regularly keeps track of what he does in his daily life by writing down all of his activities on his phone—a digital diary. Despite having no friends at school, Yukiteru is frequently seen talking to his supposedly imaginary friends Deus Ex Machina, the god of time and space; and Deus' servant, Mur Mur. One day, Yukiteru wakes up and discovers that certain events of his day are preemptively displayed on his cellphone. While initially dismissing it as a coincidence, he slowly realizes that the incidents written in his phone actually take place in the near future. After spending the day benefiting from this new asset, Yukiteru learns that his classmate Yuno Gasai possesses a similar diary. As the two team up to defeat an odd pursuer and head back to their respective homes, Deus Ex Machina explains that they—alongside 10 other contestants—have been drawn into a survival game whose victor will become the deity's successor. With no other options, Yukiteru and Yuno must use their cellphones—now called Future Diaries—to survive this unforgiving battle royale.