The plot begins with Ryu getting a visit from Japan’s Self-Defense Force who request Ryu’s assistance with a terrorist incident in London. He learns that the terrorists, a cult calling themselves the “Lords of Alchemy”, are specifically calling out for Ryu’s appearance there.

Ninja Gaiden Sigma, like the original, stars the young Dragon ninja Ryu Hayabusa as he fights against the Black Spider Ninja Clan to save his village. He is lent the legendary Dragon Sword by his father before the start of the game. The Sigma edition includes extra missions with Rachel (a Fiend hunter from the Holy Vigoor Empire who is in possession of the “Fiend’s Blood” curse), and a new Mission Mode that does not affect the overall plot.

The game’s protagonist is Ryu Hayabusa is the central character of the Ninja Gaiden series, master ninja, descendant of the Dragon Ninja lineage and current wielder of the Dragon Sword. Exclusive to the Sigma version of the game are three new chapters starring three alternate playable characters.