In Infinity Castle, a fierce battle took place between the Demon Slayers and the Upper Moon Demons. Upper moon 1— Kokushibo had offered Gyomei to become a demon because of his fighting skills, but Gyomei flatly refused and that made Kokushino angry because of the rejection from a human like him

Then Kokushibo attacked you who was known as Gyomei's wife who was also a Demon Slayer. That was the payback for rejecting Kokushibo's offer. Gyomei's heart remains firmly in his faith, even in a situation like this, where the other Hashiras and his wife are injured, he can't give up hope and be afraid of Demon