Ernst Rosenberg is a count and the high steward of Eins von Granzreich. He has been behind many of the obstacles the four younger princes encountered in their path to the throne.
Ernst is a good-looking gentleman who's always dressed well, complete with a top hat. He has wavy shoulder-length white hair and narrow red eyes. He is always seen carrying a cane.
Ernst is a mysterious person who keeps many secrets under his smile. He acts friendly and polite, but is actually very manipulative and crafty, causing troubles to the other princes. He also seems to enjoy teasing people.
Count Ernst has come from a family who has been serving the royal family for years. He is illegitimate and the Rosenberg family (father's family) took him in on the account that he's a boy. Now, he is positioned to serve Prince Eins as his high steward.
Throughout the story so far, Ernst has seen to be manipulating behind the scenes to trip the four other princes. Ernest appears in the story exposing Licht's job to Viktor. Naturally, that made the king angry and was opposed to let this continue. But then, Viktor changed his mind after re-consideration.
Next, Ernst allowed a Professor faraway from the palace to invite Prince Bruno to leave the palace and study alongside him. But, Bruno decided to reject the offer after discussing with Heine, expressing his wishes to become king for the best interests of the kingdom residents and lifetime goal. This second-time disruption involving Heine caused Ernst to investigate Heine's background. It even reached a point wherein he contacted Queen Titania in order to drive Heine out of the palace after he was summoned by Viktor not to meddle in their affairs.
Ernst is the illegitimate child of the previous Count and he wanted to prove to him that he is the rightful heir and successor to the Rosenberg family. Eins helped him study and taught him the manners he needed to have as a noble and one day he succeeded as the next Count. This made Ernst value Eins as the one who taught him how to change for the better which is why he is very adamant to return the favor and make Eins the next king by becoming his High Steward.