He learns from her that all of Gotham City's top criminals have become feudal lords after deceiving the Sengoku daimyo, battling each other until only one state remains.

When Joker's troops ambush the hideout, Batman storms his way in his Batmobile towards Arkham Castle, which transforms into a robot fortress.

He transforms his Batcycle into an armored suit to defeat Bane and stop the robot hand, only to learn the mother is a disguised Harley Quinn.

Red Hood locates Joker and Harley, but Batman discovers they lost their memories from the explosion and are living as farmers.

In a mid-credits scene, Catwoman sells weapons and furniture from the castle robots to an antique shop, while Bruce rides a horse-driven Batmobile to a party hosted by the mayor.

[9] The Nendoroid figures of Pop Team Epic characters Popuko and Pipimi, dressed as Batman and Joker respectively, were displayed at the Warner Bros. booth at AnimeJapan 2018.

It was suggested by Junpei Mizusaki at Kamikaze Douga; the studio animated both this film and Pop Team Epic television series.

The crossover figures were accompanied by a 15-second TV commercial, where Popuko and Pipimi (in the aforementioned costumes) re-enact a sketch from Pop Team Epic comics before it jumps to a Batman Ninja scene.

[14] IGN awarded Batman Ninja a score of 9.7 out of 10, saying, "DC tried something new by bringing in visionary Japanese animators to offer a refreshing take on one of the company's most beloved characters, and the finished product not only built upon the great adaptations that have come before, but surpassed them.