The only daughter of Nindo Master Tessai, Aya has trained in the Nindo arts with the brothers Kazuma and Sho since childhood. Aya would learn the art of Shinjutsu; the Arts of the Spirit under her father, and through her was taught the first part of the final Secret Art of Nindo. Fifteen years later her foster brother Kazuma would leave to seek out strength through other means, while she stayed with Sho and continued their studies until Tessai's death.
However, Kazuma, desiring the final Secret Art had her abducted by his Garzo forces in an attempt to steal the art from her. After eventually being saved by Sho, she teaches him about the final secret; it can only be attained by the merging of energies between a man and a woman. Upon learning this, Garzo Ninja abduct her and take her to Kazuma's laboratory, where Kazuma forcibly extracts the art from her despite her warnings of it destroying him in the end. After being left weakened, Aya finds herself in Sho's arms after tracking her to Kazuma's base, and gives him the key to unlock the final secret art.
After Kazuma is defeated, he sacrifices his own life to save Sho and Aya from the explosion of the fortress. Building a modest grave for their fallen family member, Aya and Sho depart.
- Aya bears similarities to Naoko from The Revenge of Shinobi, in that both are the daughter of the man who taught the protagonist the arts of Ninjutsu, and have to be rescued from an evil organization bent on world conquest.