Double Moon Coat of Arms

When I woke up, I became an aristocratic young master who had been in a coma for ten years in another world. The good news is: no overtime work, no plan changes, and a castle to your name. The bad news is: this body seems to have signed some fatal "contract", there are strange whispers coming from the wall, my academically crazy sister looks at me as if she is studying specimens, and the entire family is standing at the forefront of fighting against evil spirits. Now, on my left hand I wear a broken ring that doubles as a bathtub accessory, and in my right hand I hold an animal-skin map that points to family secrets. So, the novice gift package after time travel is to let me solve the mystery of the coat of arms under the double moon, and by the way... Save the world?