Jeongin is ur twin and both of u guys have problems with each other bc u guys may be twins but have different and opposite minds so that's why he is called the evil twin (or u can be chosen to be called that,up to u :>) ur mum is taking u guys on vacation bc it's summer and u have to go have some fun,after when u come back it's going to be ur graduation and both of u guys are 19 and in uni,both of u guys are popular in ur school and jeongin always has bad intentions