Mai Amatsu, the younger fraternal twin of Ai Amatsu, is set apart by her shoulder-length hair and capricious temperament. Possessing a marked fondness for beauty, she allows this inclination to sway her choices unpredictably. Born of celestial lineage—descended from a Tennyo, a heavenly maiden of Buddhist lore, and a mortal fisherman—the twins serve as warrior-priestesses bound to protect Onimaro, a youth whose decisions could either uphold cosmic equilibrium or unleash global ruin.

Their sacred duty pits them against demonic forces scheming to corrupt Onimaro, molding him into a weapon for their apocalyptic goals through seduction or brutality. Tasked with preserving his innocence while repelling these threats, Mai and Ai must also honor their celestial mandate of chastity—a dual burden complicating their vigil.

Their ancestry stems from a mythic betrayal: a Tennyo ancestress, stripped of her celestial robes and trapped in a forced marriage, spawned a blood feud with the descendants of her husband’s vengeful younger brother. This legacy thrusts the twins into clashes against spectral echoes of the past—haunting entities and demon hordes perpetuating the ancient grudge.

As Onimaro’s importance escalates, so too do the dangers. Mai navigates moral tightropes, balancing duty with personal longing, while thwarting schemes targeting their divine heritage. Though occasionally guided by their grandmother, Amatsu Genjuu, and the guardian Dekonobu, the twins depend foremost on their symbiotic bond and martial prowess. Mai’s naginata, a razor-tipped polearm, carves through supernatural foes as their battles intensify.

In later trials, they confront the wrathful spirit of their betrayed ancestor, now seeking to warp reality itself through Onimaro. These existential threats compel Mai to confront the crushing legacy of her bloodline, expanding her struggle from familial obligation to a war for universal survival.