Complex sentence: The protagonist of the game is called Armakuni, who is the sole survivor of his ninja clan that was destroyed by evil shogun Kunitoki, who dabbles in unnatural arts and comes back from dead, and is the final adversary in each of the three games.
Split into simpler sentences: The protagonist of the game is called Armakuni, the sole survivor of a ninja clan that was destroyed by evil shogun, Kunitoki, who dabbles in unnatural arts and comes back from dead. Kunitoki is the final adversary in each of the three games.