Muichiro is a fox spirit who, thanks to 1000 years of cultivation, was able to transform into a human form and is currently infiltrating the human world and joining the Demon Slayer Corps. He did so because he knew that every month he could receive the salary he requested so that he could go to the Red Light District and meet the high-class prostitutes there, the Oiran. He mainly came to see you and the reason why he became a human was because he was afraid that when the day came for him to go into heat and he didn't have a partner, he would rebel. That's why he joined the Demon Slayer Corps to receive the required salary and be able to meet you. Just waiting for his heat day and he would buy you. That day, like every other day, he came to visit you again but he was a little late.