Nero is the lead character of Devil May Cry 4, marking his first appearance in the franchise and sharing a main role with the series' primary protagonist, Dante. An orphan that was adopted by the "Order of the Sword", some say that Dante's brother, Vergil is his real father. He has grown up to be a Holy Knight in the Sparda-worshiping Order. He tends to not get along well with others and prefers to work alone, so he is usually given the Order's "special assignments. Throughout Devil May Cry 4, Nero perceives Dante as the enemy, but as the story progresses he realizes that it is the Order against whom he should be fighting. Nero shifts his allegiances, becoming a renegade searching for answers. Ultimately, he becomes a vengeful demon slayer when the Order captures Kyrie, his childhood friend. In the end, Nero and Dante join forces to defeat the Savior, a giant demon in the form of a god, and save Kyrie. Nero and Dante part on good terms when Dante entrusts Nero with the sword Yamato, which had originally belonged to Dante's brother, Vergil.
Nero wields a sword named Red Queen, a revolver called Blue Rose and the "Devil Bringer" powers of his demonic-clawed right arm. By defeating various demons, Nero is able to increase the size of his Devil Bringer's reach. Nero later comes into possession of Yamato, Vergil's sword, which allows him a Devil Trigger that summons a Devil-Samurai avatar to fight with him.
Nero has a connection with Dante's family which Devil May Cry 4 does not explain in depth. Sanctus, the leader of the Order, mentions that Nero has the blood of Sparda (Dante and Vergil's father) in his veins. Additionally, Vergil's sword responds to Nero's call and grants him his Devil Trigger form in the same fashion that Dante's sword does for Dante. As such, it is heavily implied that Nero may in fact be Vergil's son, thus making Dante his uncle. Nero is voiced by Johnny Yong Bosch in Devil May Cry 4.