Kan'u is a central figure in the Shin Koihime Musō universe, known by several names. Her real name is Aisha, and she also goes by the courtesy name Unchō. She is a young woman whose life was forever altered during her childhood when bandits murdered her entire family. Her older brother sacrificed himself to save her, an event that deeply imprints her subsequent actions and fuels her desire to prevent such suffering from happening to anyone else.

Driven by this profound sense of justice, Kan'u becomes a fierce and honorable protector of the weak. She travels the land, often accompanied by her close companion Chōhi, to combat the Yellow Turban Rebellion and other threats plaguing the innocent. Her reputation precedes her, earning her the title of the Beautiful Black-Haired Bandit Fighter, a name that leads many to expect a woman of stunning beauty, only to find her appearance more ordinary, a recurring source of mild personal frustration for her. She is also notably sensitive about her age and can become flustered when it or other physical aspects are pointed out.

In the anime adaptation, Kan'u wields the massive Green Dragon Crescent Blade with exceptional skill, demonstrating incredible strength, speed, and agility in combat. Her fighting style switches between fluid spear-like thrusts and devastating slashing power. Beyond her physical prowess, she is highly intelligent and a skilled public speaker, possessing a natural talent for raising morale and leading troops. Her dedication to her cause can make her a workaholic, and her straight-laced nature sometimes clashes with more easygoing personalities. Despite her bravery, she has notable weaknesses, including a fear of ghosts and an inability to cook well, though she does practice to improve. In the visual novel, her combat abilities are further explored, showing her as a master of several bladed weapons, while in the anime, she performs feats of acrobatics and raw power.

Over the course of the story, Kan'u forms deep bonds with others. She shares a sworn sisterhood with Chōhi, acting as a protective older sister and sometimes even a mother figure to her, which leads to others frequently mistaking them for mother and daughter. When Ryūbi joins their group in the second season, Kan'u initially becomes a strict role model for the reluctant ruler. Eventually, through a unique twist where she becomes the younger sworn sister, she comes to call Ryūbi aneue, or older sister. Her strong sense of honor also makes her a loyal subordinate and a formidable general. In the visual novel, her character develops from someone who rejects femininity to someone who opens up emotionally, particularly in her relationship with the protagonist Kazuto. In the anime, her strong sense of duty and her past trauma leave her inexperienced in romantic matters, though she attracts the attention of others like Sōsō.