After Isamu Fuwa sacrificed himself to defeat Kamen Rider MetsubouJinrai, the Tokyo was in peace lasted for half a month. Not for long... as the newest evil emerges: L.E.G.E.N.D. Kratt Brothers use the Drivers & Progrise Keys developed by HIDEN Intelligence to become Kamen Riders Seaspray & Springer to stop the threats made by L.E.G.E.N.D that harms both humanity and animals.

It's been a week the Team Avatar fought Fire Nation and peace has been restored. However, peace is once again disturbed in the 3 worlds: the Avatar's world, the world of Kamen Rider Saber & Wonder World. When these worlds are in danger, Team Avatar join their hands with Swordsman of Fire, Kamen Rider Saber to save them!

This is the story tells about the human and demon siblings who'll make their journey of saving the world by becoming 'Kamen Rider Demon Slayer' to combat against the villains who seek to conquer the world using the powers of the devils. (Rated 18 for violence, gore, and leaned towards mature themes)