When Taemin got lost in the wood and a storm force him to find shelter in a strange magical castle. He met a guy name Jongin who seem to be friendly. Taemin belive that Jongin is a prisioner of an evil beast named Kai who's the master of the castle.  During the day, the beast and his servants walk around the castle, but at night, only Jongin seem to be the only being in the castle. 

(this may change as I go. I'm still writting it and what I'm describing it's just the main idea. Hope you enjoy it.)