Dante, with help from Kat, slowly takes down Mundus' surgeries. During the last stages of his campaign, Dante witnesses a SWAT team raid the Order's headquarters, killing everybody in sight. Dante rescues Vergil from Limbo but he is helpless to protect Kat from being brutally beaten and hauled back to Mundus' lair. Dante then kidnaps Lilith, Mundus' demon concubine carrying Mundus' unborn child, and offers to exchange her to Mundus for Kat. During the market, Vergil kills Lilith, her child and the SWAT troops. The three allies narrowly escape as Mundus tears a lot of city apart in an outburst of power that depletes the Hellgate, a portal to the demon world within his stronghold in Silver Sacks Tower. Kat, recovering from her injuries, leads the brothers through a thorough plan to infiltrate the Towers and conquer Mundus. Dante draws Mundus from his lair and Vergil closes the Hellgate, making Mundus mortal. Mundus forms a enormous body for himself and confronts the brothers but finally, Dante lands the killing blow to destroy Mundus for good. Limbo collapses into the human world, making demons visible to people and creating chaos and pandemonium worldwide.
Following Mundus' defeat, Vergil shows his true intentions: with their family avenged, he plans to rule humanity in Mundus' place. Vergil asserts that as their saviours, they must protect humans 'from themselves' yet he callously dismisses the individual Kat's role in saving humanity. Dante is appalled at Vergil's mindset and defeats him in a climactic sword fight. Kat stops Dante from killing his brother and Vergil leaves in disgrace. Faced with a world now infested with demons and abandoned by his own brother, Dante questions his own individuality with Kat reassuring him claiming he's 'Dante, nothing more and nothing less'. The game ends with Dante's eyes glowing Nephilim Purple.
Along the way, Kat explains that Vergil leads 'The Order', a rogue vigilante organisation intent on exposing the demons and releasing the world from their own control. Vergil tells Dante that with his help the Order can bring down the demons. Dante learns that he and Vergil are not just long lost twin brothers but also Nephilim, the children of Angel and Demon and the only beings capable of killing the cruel demon king Mundus. Their demon father Sparda was Mundus' chief lieutenant in the war against the angels until he betrayed Mundus when he fell in love with the angel Eva and sired the twins. Mundus, fearful of the Nephilim, assaulted the family and murdered Eva. Sparda spirited his sons to security, wiped their memories for their own defense and gave each a sword . Mundus imprisoned Sparda and condemned him to eternal torture and has hunted Dante ever since. After learning of his past, Dante resolves to assist Vergil bring down Mundus and his regime.
The game is set in an alternate reality of this series. The game's story occurs in Limbo City, a modern-day city covertly controlled by all-powerful demons, manipulating humanity through the conveniences of life, with the demons themselves residing in a parallel plane called 'Limbo'. Living on the fringes of the brainwashed society is Dante, a young man at odds with the demons who always hunt him and the civilian police they control. Dante is cautioned by a young woman named Kat that he's in danger as a Hunter demon drags him into Limbo. Dante navigates the Bellevue Pier's carnival and kills the demon with Kat's aid, who can see into Limbo with her psychic abilities. Dante returns to the human world and takes Kat's offer to meet with her boss, Vergil.