Belle-Mere is a figure from the past of the East Blue, primarily known as the adoptive mother of Nami and Nojiko. Her story is central to understanding Nami's motivations and strength of character. Belle-Mere was born in Cocoyasi Village, where she was known as a troublesome and rebellious child. Seeking a different path, she left her home to join the Marines, rising to the rank of an officer and proving herself a capable and reliable soldier in battle.

Her life changed dramatically during a fierce battle in the Oykot Kingdom. Left gravely wounded and on the verge of death, she discovered two young orphans: a toddler named Nojiko carrying a baby, Nami. The baby's innocent smile gave Belle-Mere the will to live. She decided then to abandon her military career and dedicate herself to raising the two girls. Despite the villagers' initial doubts about her ability to be a responsible parent, she brought them back to Cocoyasi Village and retired from the Marines to start a new life as a tangerine farmer.

As a mother, Belle-Mere was a complex and deeply loving figure. Her personality was cheerful, strong-willed, and direct, but she also retained a mischievous and sometimes childish streak. She could be impulsive, reacting with her fists when her tangerines were insulted or when Nami spoke out of turn. Yet, this tough exterior masked a profoundly caring and selfless heart. Life as a farmer was extremely difficult, and the family often lived in poverty. In times of hardship, Belle-Mere would secretly starve herself, eating only tangerines and lying that she was on a diet so that her daughters could have proper meals. She supported Nami's dream of drawing a map of the world, encouraging her talent even though they could not afford the necessary books.

Belle-Mere's defining moment, and the tragic end of her life, came with the arrival of the Arlong Pirates, led by the fish-man Arlong. The pirates imposed a harsh tax on the villagers: one hundred thousand berries for each adult and fifty thousand for each child. At that time, Belle-Mere had saved just enough money to pay for either herself or her two daughters, but not all three. When Arlong and his crew came to her house, they were initially unaware of Nami and Nojiko's existence. Genzo, a close friend and the village policeman, pleaded with her to simply pay for herself and save her own life. However, Belle-Mere refused. She declared that she would pay the price for her daughters, even if it meant her own death, because she could never utter the lie that they were not her family. Her last words to Nami and Nojiko were a simple but powerful declaration of love before Arlong shot her.

In terms of abilities, Belle-Mere was a formidable fighter for a human from the East Blue. Her time as a Marine officer gave her significant combat experience and proficiency with a rifle. She was perceptive enough to sense Arlong's approach and quick enough to ambush him, briefly pinning the much stronger fish-man to the ground and putting her gun in his mouth before he could react. However, she was ultimately no match for his fish-man strength.

Her most important relationships were with her two daughters. She loved Nami and Nojiko unconditionally, a bond that was not defined by blood. She also shared a unique and long-standing friendship with Genzo, who acted as a father figure to the girls after her death. He understood her past and supported her decisions, even when he disagreed with them. Belle-Mere's legacy is not one of power or wealth, but of love and sacrifice. Her death gave Nami the initial drive to work for Arlong in a desperate bid to free their village, and her final lesson that surviving will lead to happy times has remained a guiding principle for Nami throughout her journey as a pirate. Her spirit is said to have appeared to gently nudge Nami forward when she was hesitating to leave home and pursue her own dreams with the Straw Hat Pirates.