If the player loses in any of the fights with Vyers, also known as Mid-Boss, they are treated to a hidden ending, and are awarded with New Game+.

There is a secret room in Laharl's castle. To get to it, the player must press a hidden button behind Laharl's throne, and another one on the skull on the counter of The Rosen Queen store. Then, in the big hall with Longinus, investigate the corner behind a Prinny complaining about a breeze. This will lead to Etna's secret chamber, where she will store her diary. Reading the diary in every chapter will reward you with an item called "Testament".