S. Kokubu

Shintaro Kokubu spent four years at university before turning professional, joining Ritsumeikan University in 2013 after coming through the youth ranks at Sanfrecce Hiroshima Bingo and Oita Trinita. He signed for Oita Trinita's senior squad in 2017, making 23 appearances in the J2 League over his first two seasons as a central midfielder, a role he has also played from the left wing or in a more advanced attacking position.

In February 2019, Oita sent him on loan to Giravanz Kitakyushu. Across the 2019 and 2020 seasons he made 62 appearances and scored four goals, starting in the J3 League before following the club into J2 after it won the 2019 title and secured promotion. He returned to Oita in January 2021, though his stay was brief: within weeks, on 1 February 2021, he moved on a free transfer to Montedio Yamagata.

That switch has defined his career since. At Yamagata, Kokubu has become an established presence in midfield, passing 193 appearances for the club and scoring more than 14 goals.