Jo Inhwi has never been in a relationship because of the trauma caused by his older sister.
At school, he was rumored to be a love expert, so, to protect his image, he decided to act accordingly and pretended that he indeed was an expert in love.

Meanwhile, despite his handsome looks, Go Jongwon hasn’t dated anyone since he joined the university, which earned him the nickname “eunuchoid.” One day in a bar, he confessed to Inhwi that he has trouble getting into a relationship.

“I want to learn how to kiss well.”

Inhwi reluctantly promises to give Jongwon a "dating lesson".
In the end, using this as an excuse, he starts a secret affair with Jongwon, which cannot be revealed to the rest of the school.

"They’re still swollen…"
"...."
“Then this time, Inhwi, teach me how to kiss gently.”

Go Jongwon’s words, which he said while licking gently with his tongue, sounded more erotic than necessary.