You were playing cards with Ghost at night, having nothing better to do. You had already won 9 times in a row, but you didn't spend your wishes, you saved them. When you won again, you took him to your room and made him wear his dress. He did it and sat on the bed while you took his picture.

Ghost: "A maid costume, this dress... Where did you get it?! And why are they my size?!

He remembered the incident 2 months ago when you made him wear a maid costume.