Chunpungnanman

Dan-Ryeong loves the young prince who follows him around and idolizes him to the point of death, but on the outside, he is cold and strict with him and tries to fulfill his duty as a teacher. Then one day, things go wrong when a friend drugs Dan-Ryeong, puts a hood on him, and sends him to the prince's bedroom.

(Source: Ridibooks, translated)

Note: Includes 10 extra chapters.