The Shougun Tokugawa Ieyasu is ancient and unwell yet not aged, and battle is about to break out amidst the lot of aristocrat minorities that want to see one of his grandsons, either Takechiyo or Kunichiyo, as the successor. To arrange this, each crew will be acted for by two very dominant Ninja factions, the Kouga Manjidani and the Iga Tsubagakure, who will "compete" for their cause. However, there is a huge problem.
The beneficiaries of each group, Kouga Gennosuke and Iga-no-Oboro, are occupied. It had actually been for at least ten years. Unlike other arranged couples, though, they're very much in love and were very willing to tie the knot. And this engagement was settled many years ago specifically to bring peace among their clans, who have been bitter enemies for year's ala Romeo and Juliet.