Shinobi: Heart Under Blade (2005) on Netflix

Plot summary

Two ninja clans, Iga and Kouga, have waged a vendetta for centuries, honing their skills in the mountains until they are superhuman. Around 1614, Tokugawa Ieyasu, ruler of Japan, views the two clans as a danger to his new shogunate, while Nankobo Tenkai works to deepen the rivalry between them. Ieyasu decrees a contest: each clan must send five of its strongest fighters to battle the other side to the death. Oboro of Iga and Gennosuke of Kouga, who love each other in secret and are chosen to lead the two sides, question the shogunate's motives and seek a way to stop a fight neither of them wants.