How about fictional characters falling into the real world, meeting their creators, and having battles?
For over a century, fictional characters have been falling out of their stories into our world. Some, like mech pilot Atria Silversword and isekai protagonist Daiki Yamato, want to go home. Some, like JRPG non-player character Princess Stellaria, want a new life. Some, like superhero Captain Infinite and devil king The Destroyer, want to meet their creators. Some, like monster hunter Jenny Calhoun and super-assassin Jack Death, want justice for their suffering.
And one will fight a bloody war to liberate them all.