Tsukiko hailed from a village where humans and demons lived in harmony. Her life shattered when a Mad God attacked, claiming a loved one. This loss drove her relentless pursuit of power, culminating in apprenticeship to the swordsman Shinsuke.

She possesses superhuman physical traits, weapon mastery, aura manipulation, and extrasensory perception. A key skill is Analytical Prediction, foreseeing enemy movements by observing their eyes. She wields Itakebi, a sword forged from the broken blade of Maken Arabuki, granting Electricity Manipulation. She also carries the ancient gourd of Kokugetsusai ("the killer phoenix"), enabling absorption of energy-based attacks, life-force energy, and natural catastrophes. This artifact also regulates opponents' spiritual energy, like stabilizing the Thousand Tailed Demon Fox's power to facilitate a mental invasion. Talismans augment her lightning attacks.

Tsukiko demonstrates high combat prowess, intercepting high-speed bandits and enduring prolonged engagements, such as fighting alongside Mudo against an army. Her tactical intelligence emerged early; she predicted stronger opponents' moves even in childhood. Before formal training, she outskilled Mudo in combat with Nau's assistance.

Her bond with Senya, Jinun's son and a central later figure, is profound. Initially reserved, she harbored deep feelings for him and offered steadfast support despite self-doubt. She proved crucial to his development, helping him confront inner demons and regain sanity through emotional connection. Their partnership endured conflicts, including Senya's attempts to leave her behind for safety, which she resisted. They eventually married and raised multiple children and grandchildren.

During the final battle against the Tribe of the Void, Tsukiko helped stabilize Senya's powers as he transcended into the White God. Her legacy extended far into the future, where she and Senya aged together before their eventual deaths.