Kirio is the main antagonist. He is the student body president of Sakuragaoka Academy. He tests the protagonists and fights them outside the campus. Karin refers to him as "Mr. Glasses Man." (meganekko) or "Four eyes-san." His only true relative is his twin sister Kirika, but he does have another ‘sister’ by the name of Himeka. His ring has the powers of the god Ares. (Source: Wikipedia)
