Adult Only Institute

Hyeonchang and Yoonji have sex for the first time to celebrate the 1st anniversary of their relationship. Because both of them are clumsy, sex only hurts. They remain scars to each other. Hyeonchang is suffering. With the introduction of a local senior, he enrolls in Cheongbul academy, which teaches the skills of sex. Hyeonchang learns several skills and graduates. Meet Yunji again and enjoy the sex he learned at Cheongbul Academy.

Min-cheol goes down to the countryside to focus on the foundation project. He meets Gyu-ri, a scenario writer. They fall in love and spend a hot night together but the next day she disappears. Will he be able to find the 'perfect size'?

Yonggyu and Taejun, who shoot an experimental documentary about the effects of sex on dieting, once a day with one woman! Twice a day with two women in the second week! And 3 times a day !!! No nationality, no marriage, no past?! The experiment of three weeks' reckless experiment with 6 experimental participants is unfolded. What is the end of this imaginative project?

A couples' trip to Pattaya turns into hell when each others' secrets come out into the open! Soo-jeong and Tae-hyeon decide to go abroad with Sang-jin and Ji-hyeon to celebrate Ji-hyeon's birthday. However, Ji-hyeon can't make it last minute and the three set off. However the local tour guide tricks them into losing everything they've got. Then they meet Lizzie, who Sang-jin falls for right away. They cross the line and Soo-jeong who secretly had a crush on Sang-jin, films them quietly. She then threatens Sang-jin to tell Ji-hyeon with the video of their affair and demands he takes her in. Tae-hyeon finds out about everything and the dreamy vacation turns into hell...