Be careful at Christmas! UFO-X, X-Rex... and Houtarou and his friends, who joined forces with Kamen Rider Geetz and others, made six new Level 10s at once. While everyone was in high spirits, the black steel spanner was also moving. Kyoka Edami. With her appearance as Spanner's guide, the story begins a new phase. And disaster awakens. The mythical monster ``Yamata no Orochi'' A monster resembling that giant snake fills the sky, and a darkness greater than the three sisters stands in front of Houtarou and his friends. The name of this disaster is "Grion". Kamen Rider Gatchard's biggest crisis is now upon us! !