What is the fine-grained topic of the following text: This past Monday Japanese fight fans saw a small slice of history being created as female boxing icon Naoko Fujioka (16-2, 7) [藤岡 奈穂子] defeated Mexico's Isabel Millan (18-3-1, 8) to claim the the WBA female Flyweight title and become the first 4 weight world champion from Japan. Only return the topic.
Naoko Fujioka becoming the first 4 weight world champion from Japan.