Successfully complete the game to unlock the "Relive Scene" option. This option allows any level to be replayed, including the "Release Therapy" bonus level.
Successfully complete the game to unlock a bonus level with Leo.
Get behind an enemy, then hold R1. When red, press Square.
Go to the door where the guard tells you he will not let you in because you are not a familiar face. Turn around, go off the stage, and climb up the steps on your left. Then, go up the stairs on that side. Move up the stairs until reaching the top. On the right side down the hallway is a case on the wall. Inside the case is an axe. Use the axe on a person or body. Executions immediately detach a head, where as hacking at a corpse requires a few swings. Pick up the head. Run back to the door, and equip the head as a weapon. Go to the door, and press Action. The guard will now let you in.