was a Japanese astronomer. He studied both major and minor planets, and discovered multiple asteroids.
Koishikawa was a staff member of the Sendai Astronomical Observatory frin 1972. His research was based out of the Sendai's Ayashi (391) station. The main-belt asteroid 6097 Koishikawa, discovered by Kin Endate and Kazuro Watanabe at Kitami in 1991, was named in his honor. He died on 26 August 2020 from lung cancer.