Ninjamon is a Mutant Digimon whose Japanese name and design are derived from the Iga-ryū (伊賀流 Iga-ryū? lit. "Iga-style") martial arts, and whose English name is derived from the ninja. It is a mysterious Digimon wearing a red mask. It is wandering the Digital World and building its training. It is a master of espionage, and if it is hiding within the trees of a forest, or hiding underwater, catching sight of its figure is considerably difficult. Also, although it differs in school and doctrine from Deputymon, who is also one of the "Virus Busters", they are comrades in arms since olden times, and are also good rivals.