Stephanie arrives in Edo-period Japan as a European diplomat's daughter, driven by a fascination cultivated through extensive reading in her homeland. Her romanticized view paints all Japanese people exclusively as samurai, ninja, or geisha—a naive perception that clashes with reality, causing disappointment and cultural misunderstandings. Her physical presence is strikingly distinct: an imposing stature, yellow or blonde hair, and blue eyes make her highly conspicuous, though undeterred by attention.

Exuberant yet clouded in understanding local customs, Stephanie displays boldness and a lack of restraint. She confronts a man who knocked down an elderly woman, demanding an apology and nearly escalating to violence against bystanders. Her exceptional physical strength allows her to wield a tree trunk as a weapon, making her one of the few who nearly defeats the protagonist Ran in combat. Stephanie's core motivation is to train as a samurai, believing it her destiny. After witnessing Ran's swordsmanship during the confrontation, she fixates on becoming Ran's apprentice, persisting despite reluctance.

Her enormous appetite strains finances, compounding Ran's tendency to overspend on sake and creating tension with Meow, their frequent funder. Cultural misinterpretations fuel humorous but problematic interactions, as she rigidly enforces stereotypes, insisting individuals must fit roles like "samurai-ninja" or "geisha-ninja." Frustration over unmet expectations sometimes triggers violent outbursts, though she remains earnest. Her storyline culminates in a formal duel challenge to Ran, seeking to cement her samurai status. The intense fight ends with Ran's victory via a non-lethal sleeper hold. Accepting the outcome, Stephanie decides to return home to continue her training, departing peacefully. Ran and Meow refer to her as "Suu," a simplification of her name due to perceived pronunciation difficulties.