Private secret of Na-yeon and Min-woo, the teacher who teaches herself from old times! As Min-woo's grades go up a lot, Na-yeon invites him to her house for a special class. Usually, she is a calm teacher, but her personality changes whenever she touches her body. Meanwhile, Na-yeon had another student named Jae-hyeon, who knows the relationship between Na-yeon and Min-woo and is jealous, but only enjoys the current situation. A special private tutoring class for two students and a female student, which is secretly conducted, is just beginning.

Seo-yeon likes Jin-woo, her friend since high school. She is satisfied with their current relationship where she hides her feelings and stay as a friend. Jin-woo is not greedy because he didn't have a girlfriend for a long time. Dong-hyeon, who secretly likes Seo-yeon, knows that Jin-woo and Seo-yeon like each other, but he doesn't say anything. As time went by, Dong-hyeon found out that Seo-yeon was unlikely to like him, and asked Seo-yeon to sleep with him because she will connect him to Jin-woo. The two men's mixed love between a woman is just beginning.

Na-yeong is studying to be able to find a job. Studying alone is not easy but she still spends time alone. When she found out that her friend Ji-hee's grades have improved a lot while studying, she seduced her friend Yeong-bin and took off her clothes, asking him to join her. But Ji-hee's studying was different than I thought. A study forced to have sex. Na-yeong meets Min-soo in a new study and quickly starts to adapt to a new study. Will their unique classes end well? The delicious and bitter story of two different men and women just begins.

Min-soo, who just started living in a new home, calls his friends Woo-hyeon and Ji-yeong. The two kiss while Min-soo is away from home. Unfortunately, Min-soo also secretly had sex while sleeping. And Min-soo is watching them... Ji-yeong is provoking Min-soo after learning that he saw her having sex with Woo-hyeon. Who will Ji-yeong fall in love with after having sex with these two people? The sweet and bloody story of a woman and two men is just beginning.

Dong-hoon moves to a new house. On the day of moving, he comes to the landlord to pick up the keys he didn't receive. He is happy to be seeing the beautiful Ji-hyeon. Ji-hyeon noticed Dong-hoon's interest. Dong-hoon had a housewarming celebration with his friend Min-soo. Ji-hyeon started to take a hold on the drunk Min-soo and then passed out in no time. The next day, Dong-hoon happily welcomes Ji-hyeon, who came to him without knowing what happened.

Jeong-woo, who was enjoying his honeymoon with Na-yeong, quietly calls Min-joo while she is on a business trip. And after having a lovely time alone, he was resting at home, and Na-yeong came home earlier than he thought, and Jeong-woo hurriedly sent Min-joo away, but Min-joo is hiding in Jeong-woo's house instead of going back to her house. At this time, when Na-yeong and Jeong-woo peeked at the scene, they were so surprised that they ended their relationship with Na-yeong in a hurry and drove Min-joo away. But the immature girl, Min-joo, who is enjoying this, how will their relationship end? The thrilling love story between a young man and a woman is just beginning.

At first, Yoo-jeong and Min-soo really loved each other. However, in a few months, there is a period of boredom between the two. Two people face each other and don't eat. Yoo-jeong confides her worries to her friend So-hyeon. But So-hyeon never misses the chance and confesses her feelings to Min-soo. Min-soo’s heart is shaken by So-hyeon. I'm meeting So-hyeon secretly. After a secret meeting with So-hyeon, he finds some time to relax.

Whenever she sees a messy kitchen, she calls her childhood friend Min-soo. Min-soo, complains in words but still brings side dishes to Seo-yeon. They're friends, but sex partners. Seo-yeon's relationship with Min-soo from their young age is natural. Min-soo is worried about Seo-yeon. He is jealous of the relationship between his younger friend Yeong-cheol and Seo-yeon.

Summer is almost over, but Ga-yeong who gets hot, suffers from inconvenience due to the broken air conditioner. The repairman is already fully booked and Ga-yeong is looking for someone to fix it right away. At that time, she made a reservation for a suspicious service at the store that Da-hyeon recommended the first time. There's a tremendous thing waiting for Ga-young, who will meet the driver who came from there...

Since young, Yeon-joo have a crush on her neighborhood brother, Jae-kyeong. Min-soo, had that kind of Yeon-joo in his mind. Whenever she's stressed, she would run to Min-soo A friend. A close secret with a childhood friend and the heart of Yeon-ju who loves him. Will Jae-kyeong be able to accept Yeon-joo as a woman who is younger than him? The unknown love story is just beginning.

Ji-min is married to Hyeon-soo, a married man with a child. However, Woo-yeong wasn't Hyeon-soo's own son either. The age difference is so small that she feels uncomfortable in her relationship with Woo-yeong. On the other hand, Woo-yeong falls into a sense of self-doubt that she feels love from Ji-min and that feeling from her mother, but accidentally finds out that she is an adopted child and confesses her heart to Ji-min.