Omatsu's entry into Brazilian jiu-jitsu in the mid-1990s was rooted in practicality rather than competitive ambition. A series of attacks on women in her neighborhood prompted her to seek self-defense training, and when she spotted a jiu-jitsu class at Gold's Gym in Redondo Beach, she signed up without hesitation. What began as a precaution rapidly evolved into a deep and enduring passion for the art.
In those early years, women's participation in BJJ was minimal, and Omatsu trained almost exclusively with male partners. Rather than hindering her development, that environment forged a technically precise, efficiency-driven game — one built on adaptability against larger, stronger opponents, qualities that would define her competitive identity for years to come.
A pivotal chapter in her progression arrived in 2001, when world champion Leka Vieira relocated from Brazil to the United States to lead a women's-only class at Rigan Machado's academy. Omatsu stood out as one of the group's most dedicated students, thriving under Vieira's expert guidance. In October 2002, she received her black belt from both Rigan Machado and Leka Vieira — a promotion that made her the first female grappler outside of Brazil to earn that rank in Brazilian jiu-jitsu. The ceremony carried a second historic distinction: Omatsu became the first woman in the sport to receive her black belt from another woman.
Omatsu's commitment to martial arts extended well beyond the BJJ mat. Over the course of her career, she trained in boxing, kickboxing, Krav Maga, and wrestling under world-class instructors — a cross-disciplinary approach that continuously enriched her technical skill set and competitive acumen.