Ninja Gaiden II: The Dark Sword of Chaos

This game takes place one year after the events of the original game. Jaquio's master, Emperor Ashtar, makes his appearance, seemingly having expected Jaquio to fail. Although Ashtar's master plan involves goading Ryu Hayabusa, through the use of Irene Lew, along with the Chaos Tribesmen, the reason is unclear at first.

Soon after Ashtar begins to put things in motion, Ryu is jumped by a mysterious group while spending time in the city, led by an inhuman monster named Dando. After dispatching them, he meets with U.S. Intelligence agent Robert T.S., who informs him that Ashtar has taken Irene Lew to his stronghold, the Tower of Lahja. On his way to find the tower, Ryu comes across another of Ashtar's followers, the bizarre Baron Spider. After defeating Spider, Ryu reaches the tower, and when he reaches its apex, he is ambushed by Ashtar's cybernetic monster, Funky Dynamite. After defeating Dynamite, Ashtar reveals himself to Ryu after using Irene to taunt him. Demonstrating his superior power over his subordinate, Ashtar attacks Ryu, and in doing so, paralyzes the Dragon Ninja. Before Ashtar can deliver the final blow, Robert arrives, shooting Ashtar in the back. While the shots do nothing to the Emperor of Darkness, Ashtar decides to provoke Ryu further by running off with Irene, goading him to follow him.

After the incident, Robert reveals his identity to Ryu, and tells Ryu what he knows of the nature of Ashtar's weapon, the Sword of Chaos. According to Robert, it is a powerful, demonic weapon grown from the bone of the Demon (similar to how Ryu's Dragon Sword was forged from the tooth of a dragon, giving the two swords a yin-yang-like relationship). Ryu pursues Ashtar through fiery caverns, rivers lined in bone, dungeon-like labrynths, and fields of ice. Along the way, he faces against the fossilized creature, Naga Sotuva, and is continually mocked by Ashtar. Finally, Ryu reaches Ashtar's warped, skeletal shrine, where Ashtar makes a final, grand guesture to taunt Ryu; he stabs Irene in the back, laughing as her blood drips from the sword's blade. Robert appears, and attempts to intervene, but is quickly dispatched by the dark emperor. Ashtar's true intentions are finally coming to light; his sword feeds on chaos and hatred, and he plans to power it up enough, and use it to open the gates to the Realm of Chaos, releasing the demonic hordes that reside within, and swallowing the world into eternal darkness. Ryu and Ashtar clash, and after an exhausting battle, Ashtar falls. Ashtar takes his defeat in stride, however, knowing the sword is ready to open the gate, and sends it away. Irene, struggling from her wounds, tells Ryu of an altar she apparently heard about under Ashtar's capture. Believing that Ashtar sent the sword there, she urges him to hurry and stop the ritual. Ryu leaves Irene to Robert's care, and heads off toward the altar. As he reaches the twisted temple wherein the altar resides, Robert and Irene are confronted by a new, yet all-too-familiar, foe...

As Ryu enters the temple, he once again faces Kelbeross, the demon dog twins he fought in the events of the first game. As he wonders what's going on, a wounded Robert shows up, saying that Irene has once again been kidnapped. He urges Ryu to press on, offering to hold off the approaching demonic hordes alone. Ryu begrudgingly accepts, and heads off into the temple's bizarre inner sanctum. Robert, meanwhile, fights the armies down to his last bit of ammo. It is unknown whether or not Robert survives.

At the end of the altar, Ryu finds Irene, and a familiar face; Jaquio! The sorcerer explains that he was merely a pawn back then, but after being revived by the power expelled by the Demon's defeat, he is a new man. He has taken the Sword of Chaos, after Ashtar had sent it there, and plans on accomplishing Ashtar's objective. The only difference is that he plans on expanding his power by taking in the energy that will be expelled by the opening of the gate; something Ashtar could not do, because of his sudden demise. Jaquio's plan also reveals details of Ashtar's plan; Ryu's soul was to be used to open the gate, while Irene was to be sacrificed to lure the demons out of it. Ryu, full of rage over the very sight of the man who had put him through so much a year before, launches into battle. After a grueling fight, Ryu strikes the Jaquio down once more. As Ryu and Irene have a heartfelt reunion, the blood from Jaquio's corpse pools outward. When the blood touches the blade of the Sword of Chaos, the sword fully awakens, and immediately begins to drain the power of Irene and Ryu, opening the gate. While Ryu manages to survive (possibly because of his strong will and power), Irene is not so lucky. Jaquio, however, is physically revived by the power that flows into him, but does not seem to regain his humanity. Soon, he is morphed into a massive, shape-changing beast (eventually resembling the Demon itself), before Ryu summons all the strength he has left to kill the self-proclaimed "evil demon king" once and for all.

After the battle, Ryu takes his love's body out of the crumbling temple, and laments his inability to save her. However, the Dragon Sword acts upon this, and changes into a ball of light, which circles the two, restoring Ryu's strength, and reviving Irene. Elated that Irene is alive, and that the threat of the demonic hordes of Ashtar, Jaquio, and the Realm of Chaos are finally over, Ryu and Irene watch as the day ends, and an era of peace begins.