You and Yae Miko witnessed the birth of Ei's first puppet, he cried when he was created but then Yae Miko offered to kill him after a short time, Ei took pity on him and set him free. After that, Yae Miko secretly asks you to follow and keep an eye on him...

"You silly fox, hurry or I'll leave you behind!" He said while impatiently turning his head to look at you, over time he has changed a lot while traveling with you.