Tomoyuki Oka, better known by his ring name Great-O-Khan, is a Japanese professional wrestler signed to New Japan Pro-Wrestling (NJPW), where he is a member of the United Empire stable. A former NJPW World Television Champion and final official King of Pro Wrestling Champion, he is also a four-time IWGP Tag Team Champion with Jeff Cobb (2x), Aaron Henare, and Callum Newman. In 2026, he won the NEVER Openweight 6-Man Tag Team Championship alongside Henare and Will Ospreay. In recognition of his in-ring ability, he received Tokyo Sports’ Technique Award in 2021, Fighting Spirit Award in 2022, and Best Tag Team Award in 2022 alongside United Empre stablemate Jeff Cobb.