Birds of a Feather is the first mission and it serves as a training mission as well as the first boss fight against the Man in Red. The player controls Nero and the action takes place entirely in the Opera House.
Walkthrough: Boss Fight #1
The level starts with Kyrie singing at the opera house. Nero arrives late just as she is finishing and Sanctus takes the stage. Then a mysterious assassin comes in and shoots Sanctus through the head and Nero is called to fight him. This level is simple, just follow the onscreen instructions until the Man in Red’s health bar appears at the bottom of the screen. If tutorial is turned off then the fight skips straight to the boss fight. The training section doesn't count towards the time it takes to finish the level, but any Red orbs picked up from smashing the benches do. When fighting the boss, smash as many of the benches as possible to maximize the rank. The Blue Rose is ineffective as he can bock it with his own guns, so the Red Queen and Devil Bringer to inflict damage. The man in Red only uses Rebellion and Ebony and Ivory in Human and Devil Hunter modes. He gains Coyote-A and Gilgamesh in So of Sparda and Lucifer and Pandora in Dante Must Die. Once his health bar is drained the Man in Red will flee and Credo will call you in to defend the town against the attacking demons.