Gamu Takayama is a 20 year old member of an organization called Alchemy Star. After a monster known as C.O.V attacked the Earth, Gamu falls through a portal of light and meets the giant: Ultraman Gaia, who gives him his powers.
A mysterious typhoon seems to be caused by something other than the weather, and it's up to XIG to prevent the unnatural disaster from wreaking too much havoc.
A jellyfish-like monster with incredibly destructive powers seems to be immune to conventional attacks