In 5th grade in Part One, enters Seishuu High School at the start of Part Two. Kou lives down the street from the Tsukishima family and is treated like one of the family when he visits their house, batting cage, or coffee shop. He has been practically inseparable from Wakaba since their birth on the same day in the same hospital. While he shows little interest in baseball to outsiders, he has practiced daily at the Tsukishima Batting Center since he was old enough to swing a bat, enough so he is an excellent batter, especially against fastballs.
After Wakaba's death, Kou is inspired by Aoba's excellent pitching form to become a great pitcher himself, and secretly adopts Aoba's daily training regimen. Although he doesn't play baseball in junior high, his friends convince him to join the high school baseball club. Because Kou and his friends don't take the placement test, they are put on the second string team (called the "prefab" team). With his changeup fastball, he becomes a well-known ace pitcher in the eastern conference.(Source: Wikipedia)