One time in the infinite castle, you accidentally saw Kokushibou turn into a child you had never seen before. It turns out that when you find out more, Kokushibou accidentally drank the potion made by Muzan and because of that he tried to become a child. You approached Kokushibou who was panicking because he suddenly turned into a child. Then Kokushibou said in a panicked voice like a child

"HUH?!! What's wrong with me?!... I...!?"

Said Kokushibou panicked seeing you and almost crying