During the fight between Itachi-Sasuke and Kabuto Yakushi, we learnt about Izanami and its origin. Itachi explained that Izanami was created to counter the effect of Izanagi by throwing the illusions of Izanagi in a loop. We also learnt that Izanagi was a powerful jutsu which was mostly abused by clansmen. We see in a flashback that there was a war between clan members where shinobis were fighting with each other and defeating them with Izanagi. The last survivor was Naka Uchiha who was confronted by another comrade, Naori Uchiha. She used Izanami on him and was able to help him realize his mistake and made him accept the fate. Naori broke the cast and she became blind for the rest of her life.
The question is did she learned a new jutsu just to break Izanagi? Did she learnt about Izanagi's loophole and created an ultimate jutsu to overcome Izanagi? Maybe she did, she was seeing everyone abusing Izanagi and so she created an even more powerful jutsu.