Vire has 3 attacks. He's difficult to hit with your sword unless he does his yellow ball attack, which becomes less common as the fight goes on. When he's circling you, he can be hit with a well-timed bomb.
In the first phase, manuver your boomerang so that it's on the other side of Manhandla so that you can hit all of his flowers that open. After destroying all of his flowers, he will move in a figure 8 pattern, so stand right on the edge of the side of the 3 stationary tiles in the middle and wait for him to pass over the middle. Throw your boomerang at him until he reveals his core, then hit him with your sword.