Play as Ihadurca
Beat Story Mode with any two characters, then beat it again with Setsuna.

Play as Boss and Hidden Stage
Beat the game with 3 different characters in Story mode.

Biographies
Beat a chracter in story mode to know their Background story by going into the extra option in Option menu. This will also enable the gallery mode to enjoy some nice rough sketch of the artists.

Gallery Option
Beat the Story Mode with any character.Then go to the options screen. Look for the word "Extra". Select it and you will see Gallery.

Voice Collection
Beat Story mode with any characters on the hardest difficulty level. Once you beat it with that character you will be able to hear all of that characters voices.

Congratulations Mode
Beat all modes with all characters, then go to the Options menu, choose "Extra" and select "Congratulations".

Winning Postures and Poses
Each character you beat in story mode will earn you 7 new postures.

More Costumes
To get the extra costumes for any character, beat the game with that character.