During the Edo period in Japan, a unique clan of warriors emerged, known as the Manyuu, possessing a magical skill that allowed them to reduce the size of a woman's breasts with a sword strike. In Manyuu Hikenchou, where breast size signifies status and influence, the protagonist, Chifusa, rebels against her clan's breast-centric society. She not only abandons the Manyuu clan but also steals their sacred scroll detailing breast-related techniques.
With the support of her fellow warrior, Kaede, Chifusa becomes a target for her own clan. As they navigate the dangers, Chifusa discovers a power beyond her training that could bring about significant change and equality to the land.