Saya's adopted "elder" brother. Once a popular student at school and a star athlete, he quits playing baseball shortly before Saya's arrival and has been getting into more fights at school. His father's death forces him to grow up and try his best keep his family united. He struggles greatly over Saya, and later Riku, not being human.

Initially Kai has little skill in fighting or marksmanship, but he improves as the series goes on.

(Source: Wikipedia)