Min-woo solves his sexual partner Yu-ri's financial troubles, and Sam-su-ha hires Yu-ri as Min-seok's tutor on the condition that he keeps his relationship a secret from Min-seok for the sake of his younger brother Min-seok's math grades. Min-seok gets excited when Yuri, who looks sexy his age, starts tutoring him, and he dreams of having sex that night. Meanwhile, Yuri doubts that Min-woo is dating another woman, but when she learns her door code while attending tutoring, she sneaks into Min-woo's room late at night to confirm. Yuri, delighted to see Min-woo sleeping in her room without having an affair, wakes up sleeping Min-woo and gives her a special service..