Shiro Nishi is the grandfather of Seiji Amasawa and a skilled violin craftsman. Apart from teaching courses on violin making and owning his own workshop, he also runs a small antique shop nearby to Shizuku Tsukishima's home.
Shiro is jovial and wise grandfather of Seiji Amasawa. He encourages Seiji to reach his dream to become a violin maker, and tries to convince Seiji's parents to let him train to in Italy to fulfill this dream. He befriends Shizuku after they meet in his antique shop, and shows her the Baron and the Grandfather clock, two antiques which come to have symbolic meaning for Shizuku. After Seiji leaves for Italy, Shizuku asks him for the permission to use The Baron in her book, since she knows it has special meaning to him. He happily agrees, and requests to be the first to read Shizuku's story after she's finished writing it. Although Shizuku perceives her story isn't very well written due to her lack of experience, Mr. Nishi consoles and encourages her to keep working at her passion for writing using an analogy to a geode crystal.
Shiro Nishi came across the Baron figurine in a small cafe while was studying in Germany, and was immediately taken with it. With the help of a close friend and romantic interest named Louise, persuades the cafe owner to let him buy the Baron, and to let Louise purchase his partner the Baroness when she's finished being repaired. However, before the Baroness has been returned to the cafe, World War II breaks out and Shiro Nishi and Louise were separated. Shiro and Louise never saw each other again, and the Baron and Baroness were sadly never reunited. This is why the baron statuette has such profound meaning for Shiro Nishi.