Hiroko is a nationally renowned pianist and Saki's close friend from college. Hiroko discovers Kōsei's talents and suggests Saki trains him as a pianist despite Saki's initial disagreement. Blaming herself for Saki's brutal treatment of Kōsei and his psychological trauma from Saki's death, Hiroko distances herself from Kōsei. When Kōsei returns to play the piano, Hiroko becomes his guardian and mentor.