Background
Kozuka was born in Mitsuke, Niigata.
小塚和季
Kozuka was born in Mitsuke, Niigata.
He played junior football for Mitsuke Football Club and Nagaoka Junior Youth Football Club in the Hokushin"etsu Youth League while attending Mitsuke Minami Junior High School, before being offered a spot at Teikyo Nagaoka High School on a football scholarship. Kozuka joined Albirex Niigata as an apprentice professional in 2012. He turned full-time professional with Albirex at the start of the 2013 season and made his first team debut against Tokushima Vortis in the first round of the Nabisco Cup.
On 8 July 2014, Kozuka joined Japan Football League side Renofa Yamaguchi on loan until December.
He scored his first goal for Rnofa against Sony Sendai on 2 August. Kozuka impressed at Renofa, and his loan deal was eventually extended to the end of the 2015 season.
On 6 April 2015, in the 3–0 league victory at Fujieda, Kozuka scored a 60-yard goal from the halfway line. In April 2012, he was selected in the Japan under 18 squad for the TIPOS Slovakia Cup against Norway.