Gaō is Sekiō's elder brother who is addicted to chocolate, he drools and his eyes dilute if he even smells some. He going practically rabid if he doesn't have some or he smells some on someone, attacking them if they don't give it to him. He blames Sekiō's death on Kurei and Domon, and attempts to avenge his brother by attacking Domon. He is initially defeated by Domon in the Sealed Lands arc. Afterwards he made a vow to himself not to eat any chocolate until he's defeated Domon. He reappears in Sodom and is ultimately defeated by Koganei by surrendering after he broke his vow in a fit.
He wields the bō madōgu Sekikon, which allows him to manipulate stone and is the brother madōgu of Sekichū. He main uses it to summon giant arms of stone out of the ground to grab or punch the target. He can also create armor like Sekichū. Using Sekikon takes a lot of energy, which forces him to constantly eat chocolate.
He can also conjure a powerful stone giant called Gasekiō that is durable enough to get barely a scratch from Kōgon Anki's Kiba and Minazuki forms.
While he says that chocolate is like a tranquilizer to him it actually get him even more crazy and energetic.