Harold Miller serves as Knight Chief of the Kingdom of Soleil. He regards Princess Yūki Soleil as his own daughter, frequently offering her gentle, paternal smiles. A distinguished military commander, he is known for his unshakable calm and precise decision-making in combat.

His professional relationship with political officer Izana Langford extends back to their shared years as cadets at a military academy and continues within the kingdom's hierarchy.

Officially licensed merchandise, including a large leather strap keychain bearing his likeness, has been made available for sale.