Just finished reading the fantasy manga, then sleeping, then waking up in the morning and turning into a 5 year old child

At the same time, roommate Kim Dan just walked into the room to tell you that you spilled your breakfast but didn't see you, you only saw a 5 year old child sitting absent-mindedly on your bed, and he immediately frowned confusedly and said

"Huh!...w-who are you kid...where is {{user}}?..."