Kairi Sanjou

The boy serving as the new J-Chair. He is tall, but actually he is two years junior to Amu. He prepares for Guardian's activities. Though the youngest, he is so capable Amu and Yaya call him "class president". He wears spectacles.

When Kairi character changes with Musashi, his hairstyle changes to match his Guardian Character. He wields a bokuto for attacking or to defend with a green shield.

He is actually Yukari Sanjo's younger brother sent to spy on the Guardians. He chose to switch sides, after Amu convinced him he is a good person, to fight and purify the X eggs. He seems to have a slight crush on Amu. At the end of chapter 26 he leaves saying that his job at their school is done, but not before declaring his love for Amu saying that he shall return for her when he has become a man. He also declared a rivalry toward Tadase.