The protagonist's name is Ichinose Kai (in Japan the surname is first), named after the Japanese term "ichi no sekai" (No 1 in the world).
The piano music done in the series is carried out by real-life concert pianists, specially brought on board this series.
The piano music by young Kai, young Shuuhei, and young Takako is performed by junior pianists, who were selected through a special audition hosted by Nippon Columbia.