Roo is an escaped slave who flees captivity and encounters Masato Sanada. Witnessing his strong determination and business acumen, she pleads with him to take her in. Separated from her parents during enslavement, she maintains a persistent hope of reuniting with them.

She becomes Masato's apprentice, learning trade and commerce directly under his guidance. Her aptitude for financial matters develops, though she requires the mental association of "shinies" or valuable objects to perform calculations effectively. This mentorship shapes her ambition to become a skilled money-maker.

Her character development centers on gaining confidence and practical skills within Masato's trading company. This journey reflects a transition from vulnerability to capability, driven by the dual goals of mastering business to secure her independence and finding her lost family.