A "Denjū"'s attacks cannot be altered unless a "Denjū" evolves. Evolution is achieved by three different methods: "Natural evolution" (achieved by training "Denjū"), "Modified evolution" (by giving "Denjū" certain items in a "modified evolution" area) or "Experimental evolution" (achieved by taking the DNA of one Denjū with an item called Phone Card and giving it to the "Denjū" to be "experimentally evolved"). Some "Denjū" do not evolve. In "Keitai Denjū Telefang", evolution is permanent but in "Keitai Denjū Telefang 2", evolution can be reversed if it was not achieved through "Natural evolution".