Marie Chupacabra W. Whitebear emerges as Penguin's chief rival, her deep-seated resentment rooted in a past incident involving the Nankyoku company. Her family's economic power places her as a direct competitor, constantly challenging the Nankyoku enterprise through ambitious construction ventures and strategic corporate moves. She is always flanked by her devoted subordinates, the White Knights – Maguro Hōjiro (her right-hand woman), Hunting Maria (her younger sister), Kiyomi Kodami, and Kare Ijuin – who back her every endeavor.

A major confrontation with Penguin leads to her financial ruin and bankruptcy, drastically altering her circumstances. Forced into hardship, she wears tattered clothing yet strives to maintain her dignified, lady-like bearing. Despite her reduced state, she remains envious of Penguin's seemingly effortless ability to finance reconstruction. A poignant moment arises when the White Knights organize a modest birthday celebration, underscoring their unwavering loyalty and subtly revealing her capacity to value kindness amidst adversity.

Across official media, she is known alternately as "Shirokuma" and occasionally addressed as "Kuma-san" by Penguin. Her persistence as a rival endures even after her economic downfall, demonstrating resilience in clinging to her identity and objectives.