If you are stuck in the mountain mansion level (the level where miroku walks off with some girl) this will help you. go to the right side of the room and go as far north as possible, face the wall and press x. your character will say "there are some strange characters on this wall" InuYasha will come over and say "this is human blood" and after a bit of talking you will be able to leave the room.
Submitted by Brett Hofbauer
This is how you get Co-op moves with the main character and other characters. After you do the required needs after the next battle you will unlock the combo. ( I don't work sometimes on the first try so keep on trying.)
Inuyasha- at intervals go with him 3 times.
Shippo- at interval go with him once
Sango- at interval stay with once.
I dont know the other combos for the main character, but here are character with character (Sango and Miroku).
Sango and Miroku- unlocks after your first battle with them.
Kagome and Inuyasha- use Kagome to heal Inuyasha when ever needed.
Shippo and Kagome- in interval don't chose any of those two and they might pair up. After like three times you will unlock it after a battle.
Submitted by Platinum Snake