Doukutsu Monogatari

In this platfoming adventure game, you control a little amnesiac who runs around helping out rabbit-ish creatures called Mimigas while trying to find your way out of the giant cave inside the floating island which makes up the game's setting. You can expand your health meter by collecting Life Capsules, while you can get stronger by collecting energy to boost your firearms' output. Each weapon can be built up to the maximum level (3) fairly quickly, but taking damage will drain energy from its experience meter, sometimes causing it to level down.