The Imperial family had a peculiar custom. The Empress would give the Emperor a key as a symbol of granting him her all, and the Emperor would establish their relationship by using that key to unlock and enter the Empress's chamber.

This tradition originated from an ancient Empress who seduced the Emperor by handing him the key to her chamber, and what started as a mere act of seduction eventually solidified into a tradition.

It was also a piece of lore created by the former Laura, who was the original author. Although the storyline hadn’t been fully developed and things …