To unlock the costumes below you must first beat all chapters on any difficulty. Then load your Clear Data, go to the "Gates of Hell" and the "Rodin's Treasure" menu. Then you'll see a "Super Mirror" - purchase it for 100,000 Halos and you will unlock the extra costumes. To change costumes just press RB at the Chapter Start screen in the game and go to "Costume Change".

d'Arc (Jeanne-like costume) - Purchase "Couture Bullet (d'Arc)" at Gates of Hell for 100.000 Halos.
Nun - Purchase "Couture Bullet (Nun)" at Gates of Hell for 100.000 Halos.
Old - Purchase "Couture Bullet (Old) at Gates of Hell for 100.000 Halos.
P.E. Uniform | Type A, B & C are available - Purchase "Couture Bullet (P.E. Uniform)" at Gates of Hell for 100.000 Halos.
Queen - Purchase "Couture Bullet (Queen)" at Gates of Hell for 100.000 Halos.
Umbra - Purchase "Couture Bullet (Umbra)" at Gates of Hell for 100.000 Halos.
Umbran Komachi (Kimono) | Type A, B & C are available - Purchase "Super Mirror" at Gates of Hell for 100.000 Halos.
Various | Type A (Bikini), B (Bikini) & C (Cheerleader) are available