PLOT:  Yoon Ga Young was just an ordinary high school student (16 years old, junior) who only focused on her family, friends, and studies (And even the guy she has a crush on: Changmin).  All this changed though once she was taken by a demon(?!) by force through the old tree in her family's huge backyard.  Ever since that event, Ga Young has been brought over to feudal Korea where demons were a normal thing to come across and finds out that she is a reincarnation of the deceased priestess, Tae Hee.  She also met a halfdemon named Jaejoong who was stuck on the same old tree (in feudal korea) by an arrow.  After a number of events somehow the stubborn and prideful Jaejoong and the innocent, pure, yel also stubborn Ga Young teamed up to find every shard of the blood red jewel and to defeat an old enemy who is connected to Jaejoong's past.  On their journey they also run into other enemies and allies who help them.

(Based on Inuyasha as you can see :P)