Dr. Kairo believed he needed a shinobi who would be a master Kenjutsu and Taijutsu. Though he did not support Jashinism, Dr. Kairo believed that it the most efficient way to kill someone. So while Hidan was still alive, he studied the prayers Hidan said and the rituals hidan did. He also did his own research on the religion. He then understood the religion and decided to do a "successful experiment of the Jashin religion'," on a boy from Iwagakure he kidnapped not to long ago. He then had the boy pray to Lord Jashin everyday and asked him to bless his sword so he can kill anyone Jashin asks him to. As requested Jashin blessed the boys sword and the boy became a skillful shinobi in the arts of Kenjutsu but Kairo believed if he just a shinobi who only knows Kenjutsu he will not survive long