Shinobi: Heart Under Blade.

Even though Gennosuke and Oboro are from rival ninja villages, they are secretly in love. At an annual conference with the Lord, it is dictated that a competition--a fight to the death--will take place between the five best shinobi from each village. Gennosuke and Oboro's love is made even more impossible when they each got picked as the leader of the five to represent their respective villages.