Well, that's the old Japanese term for them. They were trained, as were the males, from an early age - 4 or 5 years old - in the basic ninpo skills. Such skills including acrobatics, running, swimming, jumping, climbing, etc. Kinda like a Karate Kindergarten...
As they got older, into their early teens, they were taught many different martial arts - everything from empty hand skills to weapons to psychological warfare principles. Along with these courses came codes and ciphers, improvised first-aid, map reading, escape and evasion, blah, blah, blah.
Then the specialty training began...
The gals were taught by specially-appointed female "counselors" (read prostitutes) how to please men sexually. Along with that knowledge also came the methods to eliminate the men they were with - the ol' Black Widow routine. Poisons, knives in the head and other juicy places, garroting...all that fun stuff. They learned the ways of proper Japanese geisha, so their training also included singing, dancing, poetry, opera, cooking, etc.
All in all, a lethal troupe of little James Bondettes!