He has previously played in Nippon Professional Baseball (NPB) for the Chiba Lotte Marines from 2005 to 2008, the Hanshin Tigers from 2009 to 2013, and the Yokohama DeNA BayStars from 2014 to 2017.

On April 19, 2018, Kubo signed with the Gary SouthShore RailCats of the American Association of Independent Professional Baseball.

On July 13, 2018, Kubo was traded to the Sugar Land Skeeters of the Atlantic League of Professional Baseball.

[3] He spent the 2019 season with the club and logged an 8-14 record and 5.98 ERA while leading the league with 154 strikeouts.

[4] On December 25, 2022, Kubo signed with the Hamburg Stealers of the German Baseball Bundesliga for the 2023 season.