Iga ninjutsu(the art of the Iga ninja)
It is said that there were 25 ninja schools, of which the Iga and Koka schools were out and away the best. As Iga and Koka are adjacent, their art and skills were similar, although Iga was better in sorcery than Koka.
The reason for the development of sorcery in Iga was that since ancient times there were many exiles from the capital to the Iga basin. They had been in charge of practicing sorcery at the ancient imperial court or good at various arts such as magic and acrobatics. It is believed that they introduced the art of sorcery establishing permanent residence.
Because it was required and evolved in times of war, the art of the ninja included martial arts, stratagems, and subversive activities. Nonetheless, those which were not directly relevant to warfare accounted for a large part of their art, including psychology, pharmacy, medical, astronomy, sorcery, and divination. The art of the ninja was indeed a great collection of wisdom and skills for survival.