He described the reason for dropping out simply as "enthusiasm" when he appeared on popular Japanese television show "Junk Sports" (ja).
[8] Masato made his professional debut on March 23, 1997, against Hutoshi Takehara, winning by KO in the first round.
On March 17, 1999, he fought against Tomoharu Chiba for the vacant national AJKF title at welterweight, when he was only 20 years old.
After this bout, he was rated as #13 welterweight by World Kickboxing Association (WKA), but he announced that he was going to part with AJKF in December.
[11] He handed in a notice of withdrawal to AJKF and Fuji gym on March 14 and returned his title on that same day.
[15] He beat Takayuki Kohiruimaki, the only person who had beaten Masato before among the Japanese fighters, by unanimous decision at the tournament final.
He then moved on to the semi-finals to fight Thai kick-boxer Sakeddaw Kiatputon whom he defeated via a Right uppercut KO.
Masato finally managed to defeat Kraus via a left hook knockout in the 2nd round at 2:26 making him the new K-1 World MAX Champion.
After defeating three opponents, including Kraus, Masato lost to Buakaw by decision in the tournament finals.
On February 13, he had a press conference to announce his marriage with his wife Shin Yazawa, a Japanese actress.
Near the end of the first round, Masato connected with a left uppercut and right cross combo that knocked Buakaw down.
The first round unfolded with Kyshenko imposing his range and size on Masato, keeping him at bay throwing hard right hands and left hooks.
At the two-minute mark, Masato threw an overhand right which stunned Kyshenko, and then followed up with a left hook which sent the Ukrainian to the canvas.
Kyshenko did not make the count, sending Masato to the finals against the Dutch Shoot boxer Andy Souwer.
On October 1, 2008, Masato won his second K-1 MAX title, defeating Yoshihiro Sato and Artur Kyshenko.
[21] A K-1 Global press release on 31 December 2012 announced that Masato resigned from his position as the executive producer.
[citation needed] Masato has appeared in films such as Izo, Buyuden, Dead or Alive 2: Birds, Shukyoku Ninja and Shamo.