They charge from off screen, turns around very quickly and charge again. The window to attack them is small.
I tried shooting with Strike Needle, but they often get out of range so fast, the spread bullets do minimal damage. I tried charging swords (DTB, DA or Combuster), but it's hard to get right behind their backs to unleash it, since they start charging again so soon. And they have good HP in 4-men parties, meaning you need several attacks to kill them only for Vana to summon new ones.