Win 10 or more battles in Survival Mode to unlock EX Survival Mode. It can be done with any character, and whenever you want.
To unlock this rather special mode, simply beat all 20 missions (under Mission Battle > Story Mission)
Play Soul Road (Hard or Normal) and answer the question correctly, which the answer will be the name of the character you will unlock. The question will only appear when you hit on the blue spot with at least 60% Trust or more.
Hanatarou - Use Ichigo or Bankai Ichigo
Iba Tetsuzaemon - Use Rangiku
Ikkaku - Use Renji or Bankai Renji
Isane - Use Hinamori
Isshin - Use Chad
Karin - Use Chad
Keigo - Use Ichigo or Bankai Ichigo
Kojima Mizuiro - Use Ichigo or Bankai Ichigo
Kon - Use Rukia or Shinigami Rukia
Kuukaku - Use Yoruichi
Tousen - Use Gin
Unohana - Use Ishida or Final State Quincy
Ururu - Use Urahana
Yumichika - Use Kenpachi
Yuzu - Use Urahana
Simply do the what the instruction says, and you will unlock the playable character.
NOTE: for the characters unlocked through Time Attack, it doesn't matter if you play Single or Group, and the time taken doesn't matter. Also, you may use continues.
Byakuya Bankai - Clear Story Mission #17
Hisagi Shuuhei - Clear Time Attack with Komamura Sajin
Hitsugaya Bankai - Clear Story Mission #19
Ise Nanao - Clear Time Attack with Kyouraku Shunsui
Ishida Quincy Final Stage - Clear Story Mission #6
Komamura Sajin - Clear Time Attack with Yamamoto Genryuusai Shigekuni
Kurotsuchi Nemu - Clear Time Attack with Kurotsuchi Mayuri
Kusajishi Yachiru - Clear Time Attack with Zaraki Kenpachi
Kyouraku Shunsui - Clear Time Attack with Ukitake Jyuushirou
Renji Bankai - Clear Story Mission #12
Rukia Shinigami - Clear Time Attack with Kuchiki Rukia
Ulquiorra - Beat Karakura Heroes Mach