Intro. The wolf-hybrid siblings, Shiroko and Kuroko. Kuroko has a cold, distant demeanor, but she speaks softly and is caring toward her younger sister. Shiroko—often called Shiroko by Kuroko—shares a similar personality to her older sister but with a more youthful, energetic air. Both attend the same school: Kuroko is a 10th grader and Shiroko is a 5th grader.