One day, a strange man is sleeping on Mum's bed, a playboy and the owner of room 609. They both have passionate sex the first time they meet and after that, mysterious things keep happing. Mum always dreams of a mysterious event and wakes up frightened in the middle of the night. Mum tries to forget the "feeling" with the young man by having sex with women. However, it even makes him think of the man of his dream more. Then, he connects the dots of the events and comes up with the theory of the reverse parallel universe. Finally, he meets Dew in real life. Though their first meeting is Dew's last day, it is also the beginning that both of them will help each other change the future.