Summary

After the Infinite Crisis, the remnants of multiple Earths fused to create New Earth, which subsequently replicated into 52 identical universes through Hypertime. As Rip Hunter explained to Booster Gold, these universes existed in the same space but on different vibrational planes. A powerful entity, Mr. Mind, threatened to consume the histories of these universes, causing significant alterations to Earths over time. Despite warnings about the dangers of the Multiverse, knowledge of it spread inadvertently.

In Earth 214, an alien named Brainiac introduced mutations into the human genome, resulting in the emergence of quirks (superpowers) in 1995. As these powers proliferated, society faced upheaval, leading to the classification of powered individuals as either villains or vigilantes. By the 2050s, the most formidable villain, All For One, emerged, prompting resistance efforts that led to the creation of the One For All quirk, which was passed down through several users over generations.

Following the death of All Might in 2156, the hero community in Japan faced a crisis. Amanda Waller took control of the Hero Public Safety Commission, restructuring it as the World Hero Association and redirecting resources away from Japan. This abandonment led to rampant crime in cities like Musutafu and Hosu, which fell into chaos without significant hero intervention.

As Japan descended into turmoil, a new generation of heroes, inspired by the arrival of Superman in the United States, began to emerge. Amidst this dark period, Izuku Midoriya, who had witnessed his parents' murder in 2148, trained in secret. In 2166, he adopted the mantle of Batman at age 25, driven by a desire to restore justice to the lawless streets of Musutafu.