Saki is Kōsei's mother who was once a former pianist herself. While she was still alive, she demanded that Kōsei practice the score to absolute perfection, and often beat him up severely for making mistakes or if he didn't perform well during his concerts: her teaching methods escalated to the point where she wouldn't allow her son to play with his friends. Saki did not at first plan to make her son a pianist but after she became aware of his talent and discovered she had a terminal illness, she decided to give Kōsei a strict foundation in piano playing so he could make a living after she died.