Unlockables:

Finish Arcade Mode with Madarame Ikkaku - Unlock Yumichika Ayasegawa
Finish Arcade Mode with Ukitake Juushiro - Unlock Yamamoto 
                                           Genryuusai Shigekuni
Complete Episode Mode with Youshiro Hitsugaya. - Unlock Yamada Hanatarou
Finish Arcade Mode with Kurotsuchi Mayuri - Unlock Urahara Kisuke
Finish Arcade Mode with Ichimaru Gin - Unlock Ulquiorra
Finish Arcade Mode with Kyouraku Shunsui - Unlock Ukitake Juushiro
Finish Arcade Mode with Komamura Sajin - Unlock Tousen Kaname
Unknown; in relation to Story Mode - Unlock Soi Fon
Finish Training Mode - Unlock Shihouin Yoruichi
Unknown; in relation to Story Mode - Unlock Madarame Ikkaku
Finish Arcade Mode with Sado Yasutora - Unlock Kyouraku Shunsui
Finish Arcade Mode with Yumichika Ayasegawa - Unlock Kusajishi Yachiru
Finish Arcade Mode with Ishida Uryuu - Unlock Kurotsuchi Mayuri
Unknown; in relation to Story Mode - Unlock Kuchiki Rukia
Finish Arcade Mode with Matsumoto Rangiku - Unlock Ichimaru Gin
Unknown; in relation to Story Mode - Unlock Hisagi Shuuhei
Unknown; in relation to Story Mode - Unlock Hinamori Momo
Finish Arcade Mode with Aizen Sousuke - Unlock Grimmjow Jaggerjack
Unknown; in relation to Story Mode - Unlock Arturo Plateado
Finish Arcade Mode with Ulquiorra - Unlock Aizen Sousuke