During his time in the Hōzuki Castle, Jushiro was given a deck of cards to entertain himself throughout his life-sentence. Throughout his sentence, Jushiro became quite skilled in manipulating these cards; doing nifty tricks. Eventually Jushiro realized he could use these cards in battle, very similar to how a magician uses his own deck to entertain a crowd. But Shinobi are very skilled beings in which basic deception will usually not be enough. Because of this, Jushiro invented this basic genjutsu.