A mysterious giant capsule suddenly appears in a forgotten onsen (hot spring) town! Although, the mayor is taking pictures and looks oddly happy? Mons-Ahgar appears to throw GUTS-Select and the town further into chaos! Their hopes to save the day lie in promising new technology, and so Kanata and crew turn their efforts into combining the two GUTS aircrafts into one: the GUTS Gryphon!

The Sasamedake flower blooms. It is said to be the harbinger of disaster! Then, a golden rainbow appears in the sky! As if responding to its call, a subterranean monster appears! Ryumon is injured as this unprecedented situation unfolds. Kanata tries to cheer him up, but....what lies at the end of Ryumon's gaze?

An incident of an attacking from an unidentified monster takes place in a modern city, built where it which was once an ocean, Wadatsumi City!! Kaizaki and Ichika are immediately sent to investigate. The pair find a suspicious old woman, a mysterious girl, a crowd wearing peculiar masks, and a strange green creature. Is this a place where mysterious events gather?!