Their search for the enchantress, Morgan le Fay, takes Jack and Annie back to ancient Japan, where, in the care of a ninja master, they confront evil samurai warriors. Simultaneous. The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! Have you ever met a real live ninja? Jack and Annie do when the Magic Tree House whisks them back to ancient Japan, where they find themselves in the cave of a ninja master. Will they learn the secrets of the ninja? Or will the evil samurai warriors get them first?