After beating Rank 8, Roll calls you. Go to Roll's house and the game will state that the
door is locked. Go to Higsby shop. Stand next to Higsby and you will see something you
can go into. Go into it and press A. You will see Mai and she will ask if you want to
battle. If you defeat Roll, you will get Flower Petal V2, which lets you copy one of you
opponent's move.