You can do this with any character, win 10 or more battles in Survival mode.

Play Soul Road on hard or normal and answer the questoins correct, 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

Ishida



Ururu - Use Urahana



Yumichika - Use Kenpachi



Yuzu - Use Urahana