Shun Ukiya, the focus of the series, is a young Japanese schoolboy (who permanently wears a bandage over his nose, the only exception being his appearance in the final chapter of Gatekeepers 21) with a deep passion for kendo. Ukiya discovers that he has the ability to open the Gate of Gales in a chance encounter with an Invader attack near his hometown, where he meets fellow Gate Keeper and childhood friend, Ruriko Ikusawa. He is subsequently invited to join A.E.G.I.S. after discovering the existence of Invaders and of A.E.G.I.S. His Gate color is blue.
Skills he developed after discovering his Gate includes 'Urotora Senpuu Kiri (Ultra Whirlwind Slash)' and 'Shinkuu Misairu (Vacuum Missile)'. His Gate is considered to be among the most powerful Gates to have been discovered. He inherited the Gate from his father, and, as disclosed in Gate Keepers 21 his daughter Ayane Isuzu inherited it in turn, although she avoids using it.