After returning from a journey into the past, Batman and his allies find that their world has drastically changed. Japan, known as Hinomoto, has vanished, and the Justice League heroes are nowhere to be found. Instead, a new threat emerges as yakuza warriors descend from the skies, originating from a parallel universe. These yakuza are using an interdimensional rift over Gotham City to invade Earth, and only those who have traveled through time can see the rift's ominous presence.
Batman and Robin utilize the rift to travel to Hinomoto, where they encounter a corrupted version of the Justice League known as the Yakuza League—a criminal alliance led by the Hagane yakuza clan who have taken over Hinomoto. The Bat duo faces formidable foes such as Emerald Ray (an alternate Jessica Cruz as Green Lantern), Aqua Dragon (an alternate Aquaman), and Fleet of Foot (an alternate Barry Allen as The Flash). The Bat family fights fiercely to fend off these enemies, defending themselves with help from Amazone, a rival Yakuza faction led by Eagle Goddess (an alternate Wonder Woman).
At a crucial base, Eagle Goddess describes how the Hagane clan rose to power, corrupted by a villainous version of Superman known as Man of Steel. This corrupt Superman has abandoned the yakuza code of honor called Ninkyou, plunging Hinomoto into chaos and turning it into a battleground. Meanwhile, Harley Quinn (/actor/rie-kugimiya), from Batman's original timeline, joins forces with Eagle Goddess. She and the Joker escaped prison after learning about the yakuza invasion in Gotham, though Joker's motives are suspect as he only aids Batman to seek the opportunity to kill him.
As Batman and Robin prepare to leave for Gotham, they are ambushed by Man of Steel himself. It is revealed that Ra's al Ghul (/actor/nobuyuki-hiyama) is behind the chaos—using Gorilla Grodd's Quake Engine to manipulate reality, rewrite history, and create Hinomoto as his own domain. During this encounter, Robin is captured by the Hagane clan, and Batman is rescued by Joker and Harley Quinn. However, Joker has his own plans and flees, leaving Harley behind. Before escaping, Man of Steel warns Eagle Goddess that her alliance with Batman might lead to her downfall.
At Hagane Castle, Ra's confesses his ultimate goal: to obliterate Gotham and reshape the Earth in his image. Meanwhile, the rest of the Bat family strategizes at the Batcave to counteract the yakuza threat. The Yakuza League attacks Amazone's base, but the Bat team manages to rescue the Amazone clan and defeat several enemies, with Batman confronting Man of Steel in a fierce battle. Equipped with special gear, including a Kryptonite brass knuckle entrusted by Superman himself, Batman successfully subdues the Kryptonian villain.
The climax intensifies when Ra's activates the Quake Engine, turning it invisible and holding the key to deactivate it. As the engine threatens to destroy Gotham, the Bat family works together to disable it, with Eagle Goddess fighting Ra's alongside them. The engine's temporal paradox causes visions of heroic counterparts among the Yakuza League and Eagle Goddess, transforming them into versions inspired by the original Justice League heroes of Hinomoto. As Harley Quinn assists in shutting down the engine, the castle and the timeline are restored to their proper state, returning Hinomoto to its original timeline, and the Yakuza League members are reformed as true heroes.
With the timeline mended, Batman receives calls from the Justice League for regular weekly meetings, signaling a new era of cooperation. However, little Robin faces a humorous setback—his hairstyle from the chaos remains, and he refuses Alfred's offer to get a wig, feeling embarrassed about his new topknot.
Thus, peace is restored, but the adventure leaves lingering questions and the hope for future collaborations among these heroes.
