Duo can be tough, you just have to have the right stuff! Since you're playing Blue Moon you should have WoodSoul right? I would use his charge attack it does a little over 200 damage I believe... I would also have alot of Recovery Chips cause Duo's attacks can do quite a bit of damage. Any good P.A.s you know also come in handy... Anyway use WoodSoul's charge attack on Duo's chest to get the best effect. Now for attacks... You need to be quick to dodge most of Duo's attacks... If he raises his hands in the air he'll do one of two things... He'll either swing his in your back two rows then front two rows or after you hurt him to a certain point he'll do a fist that hits four squares. If he opens his core quickly move to the top or bottom row cause he'll shoot a beam, the beam also has rings you have to dodge (they always appear in the same pattern once you learn it it's super easy to dodge). He also shoots a face beam thing that hits 4 squares. Having Air Shoes helps in case he cracks your panels you'll still be able to move on them if they break. So basically it's all about dodging then attacking after he attacks you. Once you get the hang of his techniques you can beat Duo in no time ^-^