A former sumo wrestler for the Okayama University of Science High School, Tamura debuted in 1989 in the UWF Newborn in a losing effort against Minoru Suzuki.
[3] By this time, however, Tamura had witnessed the birth of mixed martial arts promotion Pancrase and had become interested by real fighting, like the bout he had fought against Saad.
[4] The next year, Tamura took part in the Best Of The World 1994 Tournament, advancing through the rounds by beating Bad News Allen and Naoki Sano, but being eliminated himself by eventual winner Super Vader at the semi-finals.
Unsatisfied with the symbolic return of UWF to gimmicky puroresu with the victory of Vader, and further inspired by the recent success of Pancrase, Tamura proposed to take a direction towards realistic wrestling again.
[3] The same night, Nobuhiko Takada announced his decision to retire from pro wrestling to pursue a politic career, which was met with harsh words by Tamura.
After a new rematch with Albright on August, Tamura addressed the returning Takada and challenged him to a mixed martial arts fight, to no avail.
[5] The same year, UWF International was forced by financial issues into an interpromotional feud against New Japan Pro-Wrestling, but Tamura refused to participate.
By 1995, RINGS was making the transition from shoot style wrestling to mixed martial arts and Tamura began competing actively in both.
However, in spite of his many accomplishments inside the arena of MMA, his record is somewhat marred by a preponderance of match-ups against top heavyweight and light-heavyweight competitors, including Antônio Rodrigo Nogueira, the 350-pound Bob Sapp and the former Olympic gold medalist Hidehiko Yoshida amongst others.
His later mixed martial arts performances have also been criticized as being relatively apathetic compared to the fast-paced bouts that characterized the earlier part of his career.
Part of this may owe to an absence of grappling in the bouts in question, where Tamura has often seemed more content to pursue a cautious stand-up game rather than engage in the submission exchanges he was at one point famed for.
After a scarf hold armlock submission win against Mitsuya Nagai, he faced Yoshihisa Yamamoto in the semi-finals of the 1996 Battle Dimensions Tournament.
The Japanese retaliated by threatening him with a Kimura lock, another armbar and a pair of scarf hold armlocks which almost finished the fight, but the American miraculously escaped from all of them.
The Brazilian fighter got the earliest of the fight with a guillotine choke from the guard, but Tamura started to dominate thanks to his superior striking and takedown defense.
Believing himself to be the superior on the ground, Renzo lied down and challenged Tamura to grapple with him, which the Japanese shooter did, managing to pass his guard and taking the back of the Brazilian jiu-jitsu specialist.
After returning to the standing position by the referee's order, Tamura captured the back again by reversing a takedown and locked crucifix, which he used to pursue a choke until the end of the time.
The best wrestler of the two, Tamura was able to take dominant position on the ground multiple times, but the rule against punches to the face on the mat, the referee's quick standups, and Yvel's own defensive grappling acumen impeded him from gaining the advantage.
In one instance, Tamura landed a punch which stunned Wanderlei, but it was short-lived, and the Brazilian fighter recovered and continued with the brutal ground and pound, bloodying Kiyoshi's face.
After the bout, there were suggestions for Tamura to portray the Tiger Mask professional wrestling gimmick in the Pride ring, having his first match against Ryan Gracie.
[10] For several years, efforts have been made by PRIDE to put Tamura and fellow UWFi alum and mixed martial artist Kazushi Sakuraba together in a fight due to their status as two of the best Japanese fighters of their time as well as a rumored rivalry.
Outweighing his opponent by 17 kg (38 lbs) and showing a brilliant submission defense, Tamura kept control over him in the grappling exchanges, taking his back several times and grinding him with punches and ground and pound, until he locked a stretch armlock from a keylock position in round 3 to make him tap out.
Despite the hype surrounding the fight, caused by RINGS' and Pancrase' former rivalry, the bout was swift, with Tamura outstriking him and tripping him to the mat for the ground and pound TKO.
The fight was characterized by Tamura generally countering take-down and submission attempts by Sakuraba while applying ground and pound from the top position throughout the bout.