In 1989, Sato debuted in the American Wrestling Association (AWA), where he was nicknamed the "Asian Assassin" and pushed as a cold-hearted heel. On February 7, 1989, Sato participated in a very well known battle royal for the vacant AWA World Heavyweight Championship. Larry Zbyszko won the title, denying Sato his biggest opportunity ever. Later on, Sato would unsuccessfully challenge Greg Gagne for the AWA International Television Championship. Near the end of his time in the AWA, he participated in a feud between Pat Tanaka and Paul Diamond following the breakup of Badd Company.
In early 1990, Sato, along with former rival Pat Tanaka, were introduced to the World Wrestling Federation (WWF) as The Orient Express by manager Mr. Fuji. During this run, Sato introduced the Sitout Powerbomb to mainstream American wrestling for the first time. The Orient Express kicked off a prolonged feud with The Rockers that started at WrestleMania VI and continued off and on for well over a year. The Orient Express got involved in the Legion of Doom and Demolition feud because Mr. Fuji managed both teams. Demolition was being phased out and the Orient Express took on the Legion of Doom instead. The Legion of Doom and Orient Express feud was extremely one-sided due to the Legion of Doom's massive size advantage.
After WrestleMania VI, Tanaka and Sato only made two pay-per-view appearances while in the WWF. First, at SummerSlam 1990 where the team were defeated by ”Hacksaw” Jim Duggan and Nikolai Volkoff; Second, as part of the Sgt. Slaughter-led team “The Mercenaries” (that also included Boris Zhukov). Sato was pinned by Bushwhacker Butch and Tanaka was pinned by Tito Santana only moments later. Sato wrestled his last WWF Match in 1991, where he teamed with Tanaka and “Kato" in a six-man tag team match at a house show.
In 1993, Sato made an appearance at SummerSlam as Yokozuna's flag bearer prior to his match against Lex Luger. Sato did return to the WWF in late 1994 as the white faced manager Shinja, who advised Hakushi during his heel run with the company. When Hakushi turned face, Shinja was quietly written out of the storyline. His last television appearance was on the July 24, 1995 edition of Raw, when he was piledriven by Bret Hart.