Magic Detective Agency-Catching Monster around Loch Ness

The magic detective agency ran into a juvenile help seeker who said that he saw an ogre, and the help seeker was able to describe the appearance of the monster in great detail.Although the little assistants believed that the help seeker was playing a trick, the doctor believed that he was not lying and decided to take his assistants to the scene to find out the truth.What is the connection between the Ribson River where the disappearance case took place, and the mysterious Coad Castle nearby?What is the relationship between the monster and these two?How did the members of the Magic Detective Agency reveal the answer and how did they catch the monster?