When you get Rummy in your party level her moves until she obtains high kick. When she uses it in combat Mouse will learn a move called Power Jump. When used in combat it is rather weak but if you use it in the skill menu you will be allowed to instantly warp to any place that you have a map piece for. But if you take a look at Mouse's hp after you do so you will. have lost 100 hit points but it will be no problem if Claire has her Regen chain ability.