In case you don't know, Twang is supposedly the most powerful energy blade
fighter around. You can only fight him once your energy blade rank is 35but
sometimes you'll get to battle him in class, but he goes easy, and you can
predict his attacks. Use strong attack on Twang until he glows red (usually
about 2 strong attacks make him glow). When he glows that means his next
attack is his best attack where he shoots every energy blade you can unlock
at you, usually dealing about 20-30 damage, so when he glows red then use a
defense attack and he will only do about 2-4 damage. Now then, repeat the
steps and voila! You can defeat Twang anyday! (at least almost,I think you
have a 80-90% chance of defeating him with this technique)