Rau Peipei operates as the freelance mercenary magical girl Shantoulon, a Chinese designation meaning "Two Headed Dragon." Her career began after the Distonian War, transitioning from initial employment with the People's Liberation Army to accepting CIA contracts. Primarily motivated by financial gain, she leverages her magical abilities for profit-driven assassination and mercenary operations.

Despite this profit focus, she displays protective loyalty toward Astrologer. This bond prompted her PLA defection following Astrologer's rescue from a car bombing. Peipei subsequently altered her appearance via plastic surgery and relocated to Thailand to maintain anonymity.

Initially avoiding renewed conflict with the Babel Brigade, she preferred detachment from global threats. Encouragement from Astrologer and former Magical Five comrades gradually shifted her perspective. This support realigned her motivations toward fighting for justice over monetary compensation.

Her magical capabilities include perception-blocking for identity concealment, a reactive defensive shield, and the signature finishing move "Magical Calorie Roll-Up." Her primary offensive technique, "Winds of Good Fortune," generates double-arched magical tornadoes. She wields twin nunchucks as magical weaponry and employs conventional firearms during missions, reflecting her mercenary background.

During the Ukraine arc, Babel Brigade brainwashing forced her and Tamara Volkova into conflict with former ally Asuka Ootorii. After liberation from Babel's control, she joined the New York arc, battling adversaries including duplicates of the formidable magical dragon robot Zmey.

No familial connections or parental background are documented. Her journey transitions from self-interested mercenary to justice-focused combatant, significantly influenced by bonds with Astrologer and surviving Magical Five members.