Well, the MC usually a male, so I was going with that. I don't know if Japan allows same sex marriages, anyway, which would compicate a part of the plot.
The curse of bad luck on the faimly only inflicts that bad luck on the female side(because they were Kunoichi, female ninja) and the bad luck can only be lifted by being married to one you love.
The Oni's curse, though, is particularly insidious in that respect. It forces the otherwise taciturn Kunoichi clan to seek out husbands where they would normally not(for fear of having hostages against which a demon would strike, or leving behind a grieving family if they should die) or be completely unable to continue thier duties as a Kunoichi because of the luck. However, since they have to marry someone they love(who's not family) it forbids them from using arranged marriages, which also damage the Family line's ability to preserve politcal power by forming beneficial unions. The very act of courtship for them is also frought with drama because, should they court someone, get emotionally invested, and then be in a situation where they would have thier life saved by another, the person who saved thier life would be afflicted by the curse as well. If it turns out later they can't love each other, well then all you've done in induct an outsider into the curses path, spreading it's misery.