The easiest way to beat Demon Inuyasha with Sesshomaru is to get his hp lower than yours (try to use the miasma to your advantage by always running around it but makin him run through it)then for the rest of the match run away from (just run in big circles) and make sure you don't get hit(try to have a big gap between your health and his just in case you get hit my him or miasma) trust me this is the easiest way to beat him

Attack the opponent to accrue special energy. When your character is red, spirit power is unlimited for a brief period of time, making it possible to rapidly unleash some special attacks in quick succession.

You can only fight around Black Pearl using Sesshomaru or Koga only -- the other characters cannot do this. Your oppenent must be on the edge of the battle field of Black Pearl before you jump down from the battle field. After the bird drops you back into the arena, jump up and use a fast attack (default on the X key) and you should land outside the Black Pearl. Have fun fighting and watchout for holes.

Naraku: Complete Inuyasha's Chapter in Story Mode without using any continues.
Banokutsu: Complete Miroku's Chapter in Story Mode without using any continues.
Demon Inuyasha: Complete Sesshomaru's Chapter in Story Mode without using any continues.
Human Inuyasha: Complete Shippo's Chapter in Story Mode without using any continues.
In the part of the menu where you can pick a level to play on there is a selection right before the ??? choice (or the random choice) that cannot be selected by default. Clear mission mode to unlock this stage.