There are two important family at the begining of Konoha: Uchiha and Senju. Uchiha own some amazing ability with illusion (alway called Genjutsu) and Senju have a strong body to control many
horrible power. When talking about the illusion, we alway connected it with Sharingan.
The first powerful Genjutsu is Tsukuyomi, a genjutsu that traps the opponent in a realm controlled by the user, during where days of subjective time can pass instantly, and as such allows no time for the target to break free of the jutsu. But some Genjutsu like Tsukuyomi have limit and in order to affects the five senses you have to make the man watch yours eyes directly.But Izanagi overcomed this weakness, you can across the reality and illusion, and the price is you will loss yours eye ability after that. And in this weeks naruto manga, we know that there exist another Ninjutsu called Izanami form what Itachi said. Maybeit has an unknown ability and obviously will affect the suitation of Itachi and Sasuke VS Kabuto.
If you ever know the Fairy Tales about Japan, you will know that Izanagi and Izanami are the original godness. There are brother and sister, there are the parents of Japan's legend. If Izanagi can change the reality, maybe Izanami can control the illusion, but still don't know what will pay for it after use it!