How do you unlock all characters in warriors Orochi 2 for PSP including previously unlocked?

On satge 7 on each for stories, there is a special requiremnet you must do. Wu story stage 7 - rescue Sun jian within 3 minutes Shu story stage 7 - ensure you and your allies escape the castle within 2 minutes Wei story stage 7 - defeat da Ji within to minutes after she defects Sengoku story stage 7 - defeat 1000 enemies