That same year he also hit 51 home runs, becoming the first Japanese player to break the 50-homer mark in a single season.

[citation needed] Kozuru made his professional debut at age 19 with Nagoya-gun (the team that eventually became known as the Chunichi Dragons).

Joining the Shochiku Robins in 1950 (the first year of Nippon Professional Baseball), Kozuru had a season for the ages, hitting .355, and leading the Central League in home runs with 51, RBI with a still-league record 161, and runs scored with 143.

He led the Robins to the inaugural Japan Series, which they lost to the Mainichi Orions, 4 games to 2.

[citation needed] The Robins merged with the Taiyo Whales following the 1952 season and Kozuru joined the Hiroshima Carp for the balance of his career.