She is a former Koga kunoichi who eloped with Hanzo's mentor (later revealed to also be his father). They escaped their clan since their love was forbidden by the clan's code. It's unknown how she met Earthquake but she met Galford by chance when he arrived in Japan. Seeing talent and determination in the youth, she took him in and gladly admitted him to the harsh training of Koga ninjutsu. Earthquake does the same but quits early as he lost interest. She then apparently awards Galford his muffler for completing his training years later.
She is only mentioned in the backstory and developer commentary for Samurai Shodown and Samurai Shodown II. Hanzo takes her place as their mentor in the RPG. Later, the English version of SNK vs Capcom: Card Fighters DS mistakenly credits Kaede (Hanzo's wife) for teaching them.