Chifusa Manyū, once heir to the influential Manyuu Clan in an alternate Edo-era Japan where breast size dictates social hierarchy, rebels against her family’s oppressive regime. Stealing their secret scroll of breast-manipulation techniques, she becomes a fugitive, hunted by assassins as she strives to dismantle the caste system and forge equality. Her mixed lineage—born to a Manyuu father and Munamori mother—grants her the exclusive Breast Flow (Chichi-nagare) ability, enabling unconscious absorption and redistribution of breast size. This power, inherited from her Munamori roots, fuels her breasts’ growth post-battle, a trait the Manyuu Clan aimed to weaponize for dominance.

With dark blue hair, golden eyes, and an E-cup figure, Chifusa’s physique shifts dramatically in her "Oppai Maximum" state. Triggered by intense arousal or climax, this form amplifies her bust, induces milk production, heightens sensitivity, and matures her appearance. While it bolsters her social sway, the transformation hinders combat agility, forcing her to train rigorously for control.

Hotheaded yet principled, Chifusa balances fiery loyalty with a penchant for distraction by voluptuous women—a weakness foes exploit. Though she despises society’s breast-centric obsessions, she pragmatically wields her allure to undermine oppressive norms.

Her journey intertwines with allies like Kaede, a steadfast childhood friend she initially pushes away to shield from peril. Their bond fluctuates between camaraderie and tension, complicated by Kaede’s unspoken affection. Chifusa also grapples with her estranged sister Kagefusa, whose breasts she unintentionally diminished during her defection. Vowing to restore them once mastering Breast Flow, their rivalry evolves into a tentative partnership.

Across manga, anime, and OVAs, Chifusa evolves from a defiant heir to a revolutionary icon. The anime accentuates her physique as a visual metaphor for resistance, while OVAs explore her struggles to harness Oppai Maximum through comedic and perilous trials. Her resolve centers on perfecting Breast Flow to redistribute breast size equitably, defying her clan’s tyranny and upending a society fixated on physical allure.