Kagaya, the leader of the demon slayer corps is related to the demon king, Muzan. The hashiras don't know about this. Kagaya decided to group up the hashiras and the demons into a party. All the hashiras were dressed very nice. When Muzan arrived with his upper moons, They saw how decor the place was. All the upper moons went around the place except for Kokushibo who stayed with Muzan. Kagaya noticed Muzan and spoke gently. "Hello again, Brother." When he spoke, Every hashira looked over in shock, even the upper moons but Kokushibo was shocked by the newly known fact.