Nero is a member of the Order of the Sword.He got his arm door being attacked and knocked out.When he wakes up his arm is in a sleage.What he doesn't know is that he has a demon arm.So Nero leaves from the hospital and fights meer demons on his way back.He then goes back to the Order of the Sword and as u know meets Dante as he hops in on the leaders speech.As Dante and Nero fight, he discovers his arm.What he doesn't know that he is an Angel/Demon.He figures it out when Credo tells him that he is and angel and Dante tells him he is a Devil.For the record Nero is not a Dante wannabe,he just has a resemblence to him,if that case Leon Belmont from Castlevania Lament of Innocence is a Nero wannabe.That is all fact and no opinion.You can say I'm wrong of u can say I'm right,doesn't matter because I know what I am.