Ignore the intimidating Japanese text at the outset. Fairune is simple enough to pick up. Arrow keys move you around; attacking a creature is as straightforward as walking into it; items can be used by hitting spacebar and cycling through your inventory.
It's a maze game at heart. Your progress is measured by whether you can work out where and when you're meant to use certain items to unlock new paths. Best of all, you ought to be able to finish it comfortably within your lunch break.