Kayakujutsu

 is the use of firearms, gunpowder and explosives especially by ninja.
The history and mythology surrounding ninjutsu and kayakujutsu are similar to the history of chemistry and the mythology surrounding alchemy. Thus kayakujutsu mysticism refers to "elements" like the Earth (Chi) to develop Fire (Kaji) just as alchemy referred to "elements" just as air, earth, fire and water.