Making his debut on May 2013 aged 23 Kubo has a so far mixed record of 6-1-0. Although he has been beaten previously, the future looks positive. The longest win streak that Kubo has ever recorded was between May 2013 and August 2014 when it totaled 5 wins. Kubo's longest KO streak is 2 fights long.
An explosive pro debut saw Kubo face Yodson Kamnoi in a 6 round debut fight. Shun became only the 2nd person to stop Kamnoi shy of the full distance, stopping him in the 2nd. Kubo went on to win his next 4 fights taking his record to 4 wins.
On August 22nd, 2014, Kubo was in action again beating Renren Pasignahin taking his win streak to 5 wins. Kubo's fight against Renren Pasignahin came in the 4th round of a 8 round fight via TKO. Kubo became the first person to stop Pasignahin.
Kubo went into his next career fight with a record of 5-0-0 and took this to 6 wins with a win against Nehomar Cermeno on April 9th, 2017. The win against Cermeno came in the 11th round of a 12 round fight via RTD. Kubo was the 2nd person to stop Cermeno.
On September 3rd, 2017, Kubo took on and was defeated by Daniel Roman meaning his career tally went to 6-1-0 Kubo's fight against Daniel Roman was Kubo's first stoppage defeat. This came via TKO in the 9th round of a 12 round fight. This was his latest but hopefully not last fight.