Kuze Shuuichi is Asou Renji's neighbor and a good friend to Himura Yuu. He is a womanizer and especially fond of Asou Sumire, despite her being married. Shuuichi is a famous violinist of whom Hirono Hiro is a fan. In the past, he went to the same school as Himura Yuu, Hirono Nagi, and Amamiya Yuuko; all of whom he considered to be his friends, though Kuze was planning on moving to another country by the time he met the last one.

Being a ladies man, Himura asked Shuuichi to investigate his kouhai (underclassman) Yuuko, which turned out with results, as she was the one scaring her classmates and the one who started a fight (to keep what is in her bag hidden). Before leaving, Kuze Shuuichi had a farewell party, but only inviting his three close friends at the school. However, due to their problems, none of them stayed through his entire piece (Amamiya felt his playing was too wonderful, which made her leave in tears, with Himura following her at Shuuichi's insistance), and Nagi did not even come. Later, the violinist came back to for a short time to visit an acquaintance. During this time, he sent a letter to Yuu and Yuuko, who were living together, telling them his news. While he was playing in the street, a little girl, named Hayama Mizuki, also known as Miki, was drawn to the melody from afar. When she reached Kuze, he called her a "cute little lady (kawaii ujouchan)" and tied his own hair ribbon on her head, which made Miki happy.