Kamen Rider Ryoshi: A Monster Hunter x Kamen Rider Crossover

Long ago, the advanced civilization of Babelzan created the Soulkeys, powerful artefacts that can grant humans with the power of monsters. With the power of these Soulkeys, the Hunters of Babelzan protect their people from the threat of the monsters.

However, as generations passed, greed began to consume the Hunters, as they sought to create the Ultimate Soulkey which would grant them absolute power and eternal life. They began hunting the monsters of their world to extinction, the insurmountable amount of slaughter and destruction corrupted their Soulkeys, transforming them into abominations that were neither human nor monsters. The Hunters were sealed away by what was left of their still noble brethrens, however their world has already been ruined beyond repair.

Around the middle of the 21st Century, small dimensional rifts were appearing all around the globe. Monstrous humanoids that came to be classified as Hydreads emerged from these rifts, attacking humans and converting them into one of their own for reasons unknown. The megacorporation Titancorp establish the secret organization known as GUILD to both combat and study these otherworldly threat. Their discovery of the Soulkeys and the Babelzan's technology led to the development of the Kamen Rider Project.

In the present day, 17 year old high-school student Raikou Aguri, a survivor of a Hydread attack when he was 9, was having dreams of a burning red wyvern and the Kamen Rider who had saved him and his mother from their attacker. After 8 years of relative peace, the threat of the Hydreads re-emerged in Helix City. Not wanting to let anyone else from becoming the victims of these monsters, Raikou's burning soul brought forth the red wyvern from his dream, which transformed into the Rathalos Soulkey. Using both the Soulkey and the Hunter Souldriver given to him by GUILD, the boy transforms into Kamen Rider Ryoshi, beginning his quest to hunt down all the Hydreads that threatens his family and his city.