Yoko was raised by her father, an adventurer/martial artist, and her mother, an expert in Kishibojin-Ryu Jyujutsu. Sadly, however, Yoko's parents separated when she was 10, at which time her mother gained full custody of her.
Yoko, however, is not your ordinary high school student. Her unmatched talents in Jyujutsu were discovered by the ICPO. Because of this, she gets to participate in their hand to hand combat research team.
Then one day she received a letter from her father, who was thought to have been missing. In the letter, her father requested that she acquire Ehrgeiz, the legendary weapon. At the same time, Yoko was asked to enter the Ehrgeiz tournament by the ICPO to investigate all the suspicious activities surrounding it.
Yoko is the distant daughter of Koji Masuda