Complete the indicated task to unlock the corresponding costume.

Dangerama: Complete the game, attack Darkdeath three times, and watch the ending.
Etranger: Complete the game and watch the ending.
Firo: Defeat Firo on the tenth floor of the "Baccano!" Dengeki dungeon.
Index: Defeat Index at the bottom floor of the "A Certain Magic Index" Dengeki dungeon.
Taiga Aisaka: Defeat Taiga Aisaka on the tenth floor of the "Toradora!" Dengeki dungeon.