Three nights before enlisting, Seung-wook decides to leave his mark since he can't avoid the military so he flirts with everyone. However, his school senior So-yoon nor his blind date Il-hong will fall for him. The night before he leaves for the army, Seung-wook decides he's going to see some action with the two girls. The project of 'leaving a mark' starts now.
Seong-jin, the so-called expert of theory, who learned about women through text only, feels the thrilling excitement whenever he sees his academic advisor professor, Mi-ae. However, Mi-ae keeps ignoring his courtship, telling him to come back after growing up. He felt stuck and helpless and ends up revealing his distress to Yeon-hwa, a novelist who has recently moved to his next door. To his surprise, she says she will teach him about women and begins tutoring him with the real life lessons from kissing to sex.
