Asuka is a second-year student at the Hanzo National Academy and serves as the leader of its elite shinobi team. She is the granddaughter of the legendary shinobi Hanzo, the academy's founder, a lineage that grants her immense hidden potential and a deeply ingrained sense of justice. Despite her remarkable pedigree, Asuka is known for her bright, positive, and cheerful personality. She is earnest, hardworking, and believes strongly in the values of teamwork, friendship, and protecting others. Her determination and seriousness often compensate for her occasional clumsiness and gullible nature. Because of her grandfather's teachings, she holds a somewhat pacifist view, preferring not to fight or harm others unless it is absolutely necessary, which other shinobi sometimes misinterpret as naivety given the harsh realities of their profession.

Asuka's primary motivation is to follow in her grandfather's footsteps and become a powerful shinobi while upholding her ideals of justice. She trains diligently to protect her friends, whom she considers family, and to prove herself worthy of her heritage. Her personal history includes a childhood where she frequently got into fights, until her grandfather taught her a crucial lesson about being a sword without a shield, prompting her to enroll at the academy to understand this concept. Her parents' background is unique; her mother was a ninja, while her father was a promising law student who gave up his career to be with her mother, a dedication that ultimately won over her grandfather Hanzo.

In the story, Asuka is a central protagonist whose role often involves bridging gaps between different shinobi factions. She is frequently confronted with the moral complexities of being a shinobi, particularly the distinction between good and evil. Her unwavering belief that so-called evil shinobi are not irredeemable often puts her at odds with others but ultimately helps to foster unlikely alliances. Asuka has several key relationships that define her journey. Her primary rival is Homura, the leader of the Crimson Squad. Their conflict begins due to their opposing alignments, but through their battles and shared struggles against greater threats, they develop a deep mutual respect and become close friends, though Homura still considers her an eternal rival. Within her own team at Hanzo Academy, she shares a sisterly bond with Ikaruga, whom she admires, and Katsuragi, who frequently subjects her to good-natured sexual harassment. She also gets along well with her younger classmates, Yagyu and Hibari. Another significant relationship is with Yumi from Gessen Girls' Academy. Initially clashing over their differing ideologies—Yumi believing in eradicating all evil shinobi while Asuka believes in redemption—they eventually become close friends and respected rivals after learning from each other.

Throughout the series, Asuka undergoes significant development, growing from a somewhat clumsy and struggling first-year student into a confident and powerful leader. Her potential is consistently noted to be among the highest, allowing her to rapidly improve her skills, to the point where she can match formidable opponents like Homura and even defeat legendary shinobi such as Daidōji alongside her teammates. Her fighting style is defined by her use of two wakizashi, or short swords, named Green Willow and Red Blossom. She is incredibly fast and agile, using quick, sharp attacks to overwhelm her enemies. Her ninja arts are earth-based, allowing her to manipulate the ground to create stalagmites and other barriers. She can also summon a large toad to aid her in battle. Asuka possesses a special transformation known as her Ultimate or Deep Shadow form. In this state, her hair is let down from its ponytail and she is surrounded by a green aura, which also extends the length of her blades, granting her a significant boost in power.