Nero is the protagonist of Devil May Cry 4 and is the player for most of the game. Little is known of his origins, or where he got his demonic arm from, except that Nero is a descendant of Sparda. He was orphaned at a young age and taken in by Kyrie and Credo. He was inducted into the Order of the Sword, a band of religious knights that worship Sparda. His unique talents and personality mean he normally takes care of the more unusual jobs. He and Kyrie fall in love at some point and this is what drives him on. He is sent by Credo to apprehend Dante at the start of the game, but soon uncovers a much more sinister plot when Agnus kidnaps Kyrie.
Dante, the main lead from the rest of the series is the second playable character. He is the son of the demonic lord Sparda and therefore related to Nero. He runs the Devil May Cry shop along with Lady and Trish, who hunt down demons for a living. Dante appears originally as a villain in the opening cutscene, busting into a sermon by Sanctus and shoot him through the head, although it turns out to he is a demon. After a brief confrontation with Nero he flees and Nero is ordered to track him down. He is in Fortuna to search for the sword Yamato, which belonged to his brother.
Kyrie was born and raised in the town of Fortuna. She is Credos sister and Neros lover. She is appointed as Songstress for the Festival of the Sword celebrating Sparda and is heard singing in the opening video. She often wears a necklace that was given to her by Nero. She despairs of the fact that Nero and Credo are always fighting and is upset when she finds them at each others throats. She is kidnapped by Agnus to draw Nero into the Savior, which needs the blood of Sparda to work.
Credo is the head of the Order of the Sword. He serves as a close advisor to Sanctus and dislikes Agnus. He is Neros superior and adoptive brother but doesn't get along with him that much. He changes into Alto Credo to fight Nero but loses and gives uo the Aegis shield. When he discovers that Sanctus is using Kyrie in his evil plans Credo betrays him and fights him to give Nero time to stop the Savior. Samctus stabs him with Yamato and Credo is mortally wounded. His last wish is for Dante to save Nero and Kyrie.
Agnus is a shadowy member of the Order of the Sword, specializing in demon research. A workaholic he rarely leaves his secret laboratory, leading to few people to know of his existence. His research has led him to create several demons, Bianco Angelos, Cutlass, Basilisks and Gladius. He also pioneered the ascension ceremony allowing himself and others to become angels.
Sanctus is like the Pope of Fortuna, he is the religious leader of the Order of the Sword. He is apparently assassinated at the start of the game but it turns out to be a demon in disguise. The real Sanctus is in bed setting up his real plan. His masterful achievement is the statue of the god Sparda, known as the Savior.
Trish is a compatriot of Dante and work with him at his shop. In Devil May Cry 4 she appears as Gloria, a female executive of the Order of the Sword. She is posing as Gloria to spy on the Order. She earns quick promotion due to her skimpy dress and acrobatic skills, as well as bringing the sword Sparda to Sanctus. She helps Dante evacuate Fortuna as he fights the Savior.
She appears in the Devil May Cry shop to offer Dante and Trish the Fortuna job. She later returns in a bonus cutscene to pay them. She is a fellow demon hunter and worked with Dante before in previous games.