Date Masamune is an eccentric and flamboyant character. He wears distinctive black attire and an eyepatch covering his missing right eye. His appearance features elaborate costumes, including a helmet adorned with a large crescent moon motif, reflecting his historical inspiration and dramatic flair.

He possesses a childlike, impulsive personality, frequently engaging in whimsical or absurd behavior. A primary obsession is collecting a wide array of eyepatches, ranging from mundane to bizarre designs, which he believes enhances his image. This fixation is central to his portrayal; he reacts strongly to any criticism of his eyepatches, sometimes entering a state of exaggerated despair when insulted.

Within his domain, Masamune frequently initiates eccentric projects, such as creating the anime series "Guntain," a parody of mecha genres. These endeavors highlight his impractical creativity and penchant for grand, often frivolous ambitions. Despite his self-perception as a formidable leader, his actions frequently result in comedic mishaps or impractical outcomes.

His relationships with retainers Katakura Kagetsuna and Date Shigezane are defined by their long-suffering resignation to his antics. They often observe his behavior without intervention due to familiarity with his erratic nature. This dynamic reinforces his portrayal as a whimsical figure whose retainers prioritize damage control.

Masamune occasionally displays delusional self-importance, comparing himself to cultural or historical icons. His speech and mannerisms feature theatrical declarations and exaggerated confidence, though his actual competence in governance or strategy is minimal. This gap serves as a recurring source of humor.

The character remains consistent across media, maintaining his core traits of flamboyance, eyepatch obsession, and comedic ineptitude without significant evolution. His role primarily serves as a parody of the historical "One-Eyed Dragon," exaggerating traits like ambition into absurdity.