Set in the Sengoku period -- a time characterised by warring factions and constant social upheaval -- the story is centred around Oda Nobunaga's sister, Saku. As the princess to Owari Province, she is arranged to be married off politically by her brother to Oumi, in order to solidify the two provinces' ties.
But Saku despises the idea of being married to a man (preferring women in bed instead) and hates the idea of leaving her home province. During an argument over Saku's apparent interest in taking a bride instead of being married off as one, Nobunaga flatly tells Saku that it is preposterous, as two women cannot conceive children with one another. In anger, Saku retorts that it is possible, and her brother sarcastically agrees to call the marriage off if she manages to conceive a child with a woman.
Saku then acquires a strange drug from a vendor that will apparently let her do just that, and in desperation, she takes the drug without knowing what its exact effects are. That night, she finds out she's grown a penis and has a much stronger libido than before. The rest of the story depicts her attempts to manage her sexual desires, hide the secret of her new genitalia from others, and work in the shadows in order to thwart the impending marriage and what she perceives as her brother's betrayal.
As Saku has a very dark and sadistic side, most of the sex scenes from the first half are more or less non-consensual and include mental torment, evolving into either consensual sex or greater sadism (including physical abuse) in the latter half depending on your choices. Despite the high sexual content, this title has a fairly substantial and logical storyline, and is probably suitable for those who like futanari, violation with/out physical abuse, sex scenes without any male characters' involvement (except for one in a bad end), (futa)girl/girl love, feudal Japan, and political intrigue. Buried under everything else, there is a love story here, where love manages to quell the raging darkness inside Saku's heart.