A single battle changes everything.

While pursuing a powerful Upper Rank demon through a remote forest, members of the Demon Slayer Corps are caught in a mysterious Blood Demon Art unlike anything they've encountered before. Instead of trapping them in an illusion or another location, the technique tears open reality itself, pulling them into a completely different world.

When they awaken, they're no longer in Taishō-era Japan.

They're in modern-day Yokohama.

Towering skyscrapers replace mountains, speeding cars replace horse-drawn carts, electric lights illuminate the streets, and ordinary civilians walk freely without fear of demons. But something feels wrong. The demons they were chasing are gone... yet supernatural abilities unlike Breathing Styles exist everywhere.

After a chance encounter with the Armed Detective Agency, the Demon Slayers learn that this world is protected not by swordsmen, but by gifted individuals with extraordinary abilities. As the mystery behind their arrival deepens, strange creatures begin appearing across Yokohama, and it becomes clear that the dimensional rift hasn't closed.

Now, two groups of protectors from entirely different eras must work together to stop a threat that could merge both worlds—and bring demons into a society completely unprepared to face them.