Yūji Koseki (古関 裕而, Koseki Yūji; August 11, 1909 – August 18, 1989) was a Japanese ryūkōka, gunka, march, fight song and film score composer. His real name was also Yūji Koseki, but its kanji was 古關 勇治. For his contributions in music to baseball, he was inducted into the Japanese Baseball Hall of Fame in 2024.
Source: “Yūji Koseki”, English Wikipedia (CC BY-SA 4.0), excerpt