Something among the lines of this (lifted from another forum) - Some Time Before The Game Begins:
Izuna Jinkuro kills Oboro and all of Oboro's other students, becoming the last living practitioner of Oboro Style swordsmanship. Torahime (sister to Momohime) becomes a shrine maiden at a temple dedicated to safeguarding a powerful Demon Blade (Kuzuryu) that can transform its wielder into a god.
Shortly Before The Game Begins:
Jinkuro somehow comes into possession of a Demon Blade (Kuromitsu) that allows its wielder to steal the bodies of others. During this time he is cursed (detailed in the 1st DLC). Momohime is engaged to marry Yagyu Yukinojyo. Kisuke infiltrates Torahime's shrine on behalf of his ninja clan, intending to steal the Kuzuryu, but finds himself falling in love with her.
As The Game Begins:
Jinkuro attempts to use Kuromitsu to steal Yukinojyo's body, but misses and accidentally possesses Momohime instead. Yukinojyo manages to steal Jinkuro's Demon Blade and spirit it away in the confusion. Kisuke betrays his ninja clan and attempts to prevent the theft of Kuzuryu; he fails, and is mortally wounded in the process. He bargains for his life with the ghost of Oboro, who performs the Spirit Transfer technique, healing Kisuke and granting him mastery of Oboro Style swordsmanship, but destroying his memory - and Oboro's soul - in the process. Torahime is killed shortly thereafter while attempting to recapture her Demon Blade. She bargains with the gods to be temporarily resurrected in order to continue her quest.
During The Game:
Momohime: Jinkuro (in Momohime's body) pursues his lost Demon Blade, eventually storming the gates of both Heaven and Hell, to no avail. Ultimately, he gives up on recapturing the blade and decides to challenge the gods themselves - ostensibly to gain a new body for himself, but secretly he also wishes to save Momohime, whose body is dying as a result of the botched possession.
Kisuke: Kisuke slowly pieces together his past. Meanwhile, Torahime's Demon Blade makes its way into the hands of the Shogun, who plans to use it to become a god. Kisuke eventually joins the resurrected Torahime's quest to recapture the Kuzuryu; it's not entirely clear whether they rekindle their former romance during this time.
Now for the Endings (Due to the nature of the matter, all SPOILERS are unmarked, BEWARE!). Normal Endings:
Momohime: Jinkuro puts up a good fight, but is ultimately no match for the gods. On the brink of death, he bargains for Momohime's life; Momohime is healed, while Jinkuro's soul is consigned to hell. Thoroughly traumatised by the whole affair, Momohime breaks off her engagement with Yukinojyo and becomes a nun.
Kisuke: Torahime challenges the Shogun alone, and is mortally wounded. Kisuke arrives just in time to witness her death. He challenges and defeats the Shogun himself, then extirpates his shame at being unable to protect Torahime by committing seppuku. Torahime once again bargains with the gods to allow both herself and Kisuke to be reincarnated on Earth; it's implied that their romance repeats itself in the next life (with a little divine encouragement).
In either case, Oboro Style swordsmanship becomes extinct.
First Unlockable Endings:
Momohime: When Jinkuro arrives at the summit of Rankai's temple, he finds Kisuke waiting to stop him, rather than a contingent of gods. Presumably, this ending takes place in an alternative timeline in which Kisuke did not commit seppuku following the Shogun's defeat, and went on to have other adventures. Jinkuro kills Kisuke, but Momohime's body is mortally wounded in the process. As a final "screw you" to the gods, Jinkuro destroys his soul to perform the Spirit Transfer technique for Momohime, just as Oboro's ghost did for Kisuke; like Kisuke, Momohime's wounds are healed, but she loses her memory. Later, an amnesiac Momohime discovers her granted mastery of Oboro Style swordsmanship while defending her adopted village from a terrible oni, and goes on a quest to discover the truth of her past.
Kisuke: When Torahime arrives at the Shogun's palace, she finds that the Shogun is already dead, and that Jinkuro - still in her sister Momohime's body - has taken his place. Apparently, in this alternative timeline, Jinkuro got wind of the Shogun's plans and decided to take his place and ascend as a god himself rather than storming heaven. Kisuke uses Oboro's Secret Arts to cut away Jinkuro without harming Momohime, destroying Jinkuro's soul. Torahime lives out her few remaining days in peace; after her death, Kisuke becomes Momohime's servant, and they have numerous adventures tracking down and destroying the remaining Demon Blades.
In either case, whichever character you're playing as - Kisuke or Momohime - becomes the last practitioner of Oboro Style swordsmanship.
Second Unlockable Ending:
Momohime: The Muramasa Oboro transports Jinkuro back in time to just before his botched confrontation with Yukinojyo. Using his memories of the future, Jinkuro avoids the confrontation, and quietly assassinates Yukinojyo and steals his body at a later date, faking his own death in the process. In the guise of Yukinojyo, he marries Momohime. The text of the epilogue indicates that they have three kids and live out the rest of their lives in quiet obscurity.
Kisuke: The Muramasa Oboro transports Kisuke back in time to some point after Oboro performed the Spirit Transfer technique, but before Torahime's Demon Blade was spirited away by the Shogun's men. His memories of the future allow him to easily capture the Kuzuryu for himself, whereupon he runs off with it to have adventures across the sea or something. The text of the epilogue jokingly promises a further twenty sequels detailing those adventures.
