Ayame's Iris was a spiritual flower used by Ayame, the young wolf yōkai. In Episode 84, she used this pin to save Kōga from a hair demon who nearly devoured his arm. In the same episode, Miroku shouts "it's the spiritual power of the Iris!" and also in the flashback of Ayame and Kōga, Ayame explains that the Iris flower will help her in her training. Since Ayame is an anime-only character, she was never revealed in the manga.
- Iris on Wikipedia