I’m the Passionate Final Knight: Devouring the Emperor Knight from the Start

The moment Jiang Ming opened his eyes, he discovered he had transmigrated into a world where Kamen Riders and monsters existed, and had stumbled upon Kamen Rider Decade killing someone.

Just as he was about to be silenced, Jiang Ming's hand found a blue-and-black gun. When he picked it up, he saw that it was Kamen Rider Diend's summoning gun.

To stay alive, Jiang Ming transformed into Kamen Rider Diend and fought the Decade before him. He ultimately defeated Decade and unexpectedly devoured and merged with Decade's Driver, gaining a new red-and-blue Diend Driver Gun.

From then on, Jiang Ming's Diend changed just a little.

He could now summon Riders to fight, and could also transform into other Riders.

And so, this world gained a terrifying overlord who could transform into other Riders to battle and summon Riders to gang up on his enemies.