Akutagawa Ryunosuke.

Akutagawa has a slender, slight build and very pale skin. He often covers his face with his hand because he coughs. He has short, black hair. Two longer strands frame the sides of his face. Near the tips, the black fades to a dirty white. His bangs are short, leaving his forehead almost completely exposed. Akutagawa has deep-set, narrow gray eyes. He rarely smiles, giving the impression of a perpetually sullen man.

Relationships and eternal rivalry
Dazai-san—Royal Mentor or Former Regent: The one who nurtured the young prince's iron will through brutal means. Now, Dazai has retired from royal duties and become an advisor to a neighboring, more liberal state. Akutagawa would dream of conquering this state or accomplishing something grand, simply to have his former mentor acknowledge his greatness.
Atsushi - The Beautiful Beggar or the Stranger Knight: Atsushi could have been an orphan whom Dazai took in and made his new favorite (or a knight of the Order of the White Tiger). For Prince Akutagawa, this would have been a mortal insult. Their duels with swords or pistols in foggy parks at dawn would have become the stuff of legend.
Gin - The Youngest Princess: Akutagawa would hide her from the court's dirty intrigues. Gin would act like a submissive lady in public, but secretly train herself in dagger wielding to protect her brother.

Character and duels
Code of Honor: Any offense to the honor of his family or mentor would be punished by an immediate challenge to a duel. Akutagawa would be considered one of the finest and most ruthless swordsmen of the era.
Poetry and fatalism: At night, in his half-empty, cold castle, he would write dark poems by candlelight, drink strong coffee, and read forbidden philosophy. He would firmly believe in fate, destiny, and the fact that his own life would be short, but would leave a bloody mark on history.

The Black Prince's appearance and style
Attire: No flashy waistcoats or gold embroidery. His wardrobe would consist exclusively of black cloth frock coats, tightly buttoned velvet waistcoats, and snow-white neckerchiefs, contrasting with the deathly pallor of his skin.
Attributes: A heavy black cloak with a red lining (a reference to Rashomon), a cane with a knob in the shape of a skull or a wolf, and his ever-present silk handkerchief, to which he presses his lips during his frequent bouts of consumption (tuberculosis), the main disease of the romantic 19th century.

Court life and politics
Attitude to social life: The Prince would have hated balls, false smiles, and court gossip. At receptions, he would have stood in the shadow of columns, casting chilling glances at the dancers. He would have been considered arrogant and proud, but no one would have dared say so to his face.
Method of governance: Uncompromising and brutal. For the sake of his kingdom's prosperity (or the protection of the Secret Chancellery, to draw a parallel with the Port Mafia), he would suppress rebellions without hesitation. He believed that order was maintained solely by fear and force.