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Gaap wears the typical school uniform at Babylus except that he doesn't have the complete bow tie (having only the button-like demon eye ornament), nor the side pockets. He also has a belt-like strip of cloth along his waist where he keeps his sword. His collar is folded much like Purson Soi's and his coat is longer than the standard, almost reaching his knees. His hair is silver and looks very close to Kerori's natural hair color. His skin also seems to be of the same color.
Kamaitachi (Wind Sword) (風太刀（かまいたち）): Gaap's inherited magic from the Goemon family. He can create invisible blades from the wind with extremely flexible movements. These blades could also be thrown similar to a boomerang.
Wind Blade: Kill: Gaap gathers wind until it became concrete and connects with his sword and quickly lashes it out to the opponent or an item and cut it in half. These winds whirls around the sword and maintains a light blue color until the sword is sheathed back.
Rescue Gale: An enhanced version of Wind Blade Gaap learned while training for the Harvest Festival. Allows him to strike opponents over a wide area but leave allies unharmed.
It's revealed in chapter 111 that he befriended Agares even before they were paired up for the Harvest Festival. The two seem to be good friends, though Agares was reluctant at first.
He was assigned alongside Agares to Lady Vepar, whose plan is to enhance their bloodline abilities. She emphasizes that their abilities are strong, but only on the ground, so she trains the two to overcome situations where they cannot use their abilities by trapping them underwater (Vol. 12, Ch. 95-96, & 98).
In demonology, Gaap (also spelled as Goap and Tap) is a Prince of either the southern or the western zone of Hell (President or King in some versions). He can teach philosophy and all liberal sciences, cause love or hate, make men insensible and invisible, deliver familiars out of the custody of other magic-users, give true answer concerning the past, present, and future, carry and re-carry men and things from one nation to another at the summoner's will, and can make men ignorant. He also has control over the Water Elementals or 'water demons'. He is said to be better conjured to appear when the Sun's in a southern zodiacal sign, and should be honored with sacrifices and burning offerings. He is depicted in a human-like shape.
In one of his early chapter appearances, his apparent 'fur' blows in the wind and reveals what seems to be a humanoid chin.