>>279993290
Sakura referred to it as "分身の術" or "bunshin no jutsu" which means "other-self technique". This technique is usually associated with ninja and it a bit of a classic reference. Foxes obviously do it too. Rokumon referred to 狐幻術 or "kitsune genjutsu".

Another term is "かげぶんしん" which means "shadow other-self" basically.