In March 1987, Tuli was recruited by Takamiyama Daigoro, another Hawaiian, and joined Azumazeki stable, which Takamiyama had founded the previous year. He was unbeaten in his first 14 official bouts, winning two consecutive tournament championships. Weighing nearly 200 kg (440 lb), he was one of the largest wrestlers in sumo. In March 1988, he was promoted to the third highest makushita division, and became the first foreign born wrestler to ever win the championship in that division. In the same month, future yokozuna Akebono Tarō, also from Hawaii, joined Azumazeki stable. As the highest ranking wrestler in the stable, he was a mentor to Akebono and gave him advice on how to adjust to life in Japan. In March 1989 Takamikuni reached his highest ever rank of makushita 2, and even fought two bouts with elite jūryō ranked wrestlers (one of whom, Tōryū Kenji, was a former sekiwake). Takamikuni was never to reach sekitori status himself. He did not compete in the following tournament, and retired from sumo in July 1989 due to knee problems.
After leaving sumo, he competed as Teila Tuli in the first bout of the UFC 1 in November 1993, held in Denver, Colorado. It was shown on pay-per-view. Despite heavily outweighing his opponent, he lost to Gerard Gordeau, the match being stopped after Tuli was kicked in the face causing the loss of a tooth. This was Tuli's only MMA fight.The match has been described as one of the top five David and Goliath match-ups in MMA history.