Introducing Kairi Sanjo (三条 海里, Sanjō Kairi)

Kairi Sanjo replaces Kukai as the new Jack's Chair when Kukai leaves for middle school. Kairi is tall, despite being two years junior to Amu. Unlike the spontaneous Kukai, Kairi is uptight, very organized, and blunt about faults. Even with these traits, he is so capable that Amu and Yaya call him "Class President"

Kairi is the younger brother of Yukari Sanjo and was sent to spy on the Guardians. This wasn't his choice though, as Yukari immediately begged him to transfer to Seiyo upon discovering that he had a Guardian Character. Since his sister is busy at work, Kairi takes care of the household work (and his sister) in her apartment. However, when he saw the true meaning of his "missions," he tries to rebel against Yukari, but not before he reveals his secret to the Guardians when they accidentally discover him with Pestering CDs. He switches sides after Amu convinces him he is a good person. Afterward, he leaves saying that he promised his parents and local classmates that he would return, but not before declaring his love for Amu, saying that he shall return for her when he has become worthy of a man. He also declared a rivalry toward Tadase. Recently in Chapter 44, he is shown in Amu's town looking for Yukari and comments about also looking for "that person". In chapter 45, he becomes the adviser for Yuu Nikaido and Yukari Sanjo, who are arguing about getting back together. In chapter 46, he returns to the academy to meet with Tsukasa, meeting Hikaru and Yaya on his way. In the anime television series, Kairi is voiced by Mitsuki Saiga. He is portrayed by Reo Sawada in the musical.