On her deathbed, Nadeshiko's mother, Natsume, revealed to her the history of their clan. Clans.
The Iga and the Koga, as far as can be remembered, hail from the Land of Demons, far to the west. It is a strange and mountainous place, filled with spires of stone like fingers poking up from the earth and stabbing into clouds- smaller, wispier clouds weave through like strands of hair. It is said that the Tengu, those god-beasts from which Shinobi gained their original arts- before the Sage of Six Paths walked the earth, there were Tengu, and after the Sage, there were Tengu, and it is from them that the Clans learned their skills, so long ago.
Who would notice a shadow of a tree, or the stone on the mountain? No one.
Natsume, in her old age, had forgotten which clan she was from. Forgotten, even, her daughter's name- called her Kagome (Kikiyo, Midoriko, remember how to fly away), called her San (wolf girl, wolf princess), called her "cousin", "auntie", "little sister", "mother"- but she told her. Of their family's past- their skill as ninjas in the truest fashion, of the age before the Daimiyo's, when the Emperor of Heaven still walked this earth. Gone now, of course- but it had been.
And they had survived by remaining hidden, from all that would see them. Tengu, even when the true tengu, so old and powerful, died out and vanished in a world grown too mad and bloodthirsty for their kind of night.
In her old age, on the bed of her death, Natsume, mother to Nadeshiko, apologized as best she could for training her daughter to be a fine kunoichi. A ninja in the most subtle of ways. As her clans would have named her- a Tengu.
Over the years of her training, Nadeshiko was taught all the skills her mother still knew and could teach of the Iga and the Koga- tree walking, water walking, ninjutsu, genjutsu, taijutsu, kyujutsu, seduction arts, poisons, medicines, manners and deportment. Forgery. Mathematics. Arts. Sciences. Everything she could burn into her daughter's soul she did, regardless of the harm she did her daughter.
There, on the eve of her death, with her last rasping breaths, she apologized to her daughter for treating her so… and rasped out the history that she hoped would live on in her daughter's veins.
She died without ever actually saying "I am sorry" to her daughter.
Nadeshiko is contemplating her heritage, her mother, and her daughters as she darts, quiet and forgettable- forgotten- through the haze and screams of a battle field. Leaves fighting Stones, and neither side notices her dark form darting through the blood and ash stained lands. In that moment, of being unnoticed as all Iga and Koga ninja were, are, must be- in that moment, when protecting her daughters is more important than hiding, because of course those Stone ninja have a sensor with them, of course they do- in that moment of battle rage and decisive action, Nadeshiko realizes that she is, above all, grateful to her mother for teaching her as she did.
She also has the time to curse the gods for allowing a group of Leaf ninja to stumble across her when she's too tired to fight or flee.
Still. Of all her prospects, joining Konohagakure during the calm before a war is perhaps her least onerous. And deadly.
So she did.