
The move comes after 16 years and 54 fights in the welterweight and middleweight divisions.
The highlight of the 35-year-old's career was his 2006 run in PRIDE's 183-pound Grand Prix where he defeated future champions Hector Lombard (Bellator) and Gegard Mousasi (Dream and Strikeforce).
Caol Uno and Mitsuhiro Ishida are two other recent Japanese names moving down in weight, both to featherweight after lengthy careers as lightweights.
Sengoku announced Tuesday Gono's fight as well as a welterweight tournament reserve bout between Motoki Miyazawa and Takuya Sato. The current card is below, in reverse order.
Sengoku Middleweight Title
Jorge Santiago vs. Kazuo Misaki
Lightweight Bout
Akihiro Gono vs. Jadamba Narantungalag
Welterweight GP
Taisuke Okuno vs. Nick Thompson
Kenta Takagi vs. Yasubey Enomoto
Motoki Miyazawa vs. Takuya Sato (Reserve)
Asia Bantamweight Tournament
Jae Hyun So vs. Hirokazu Nishimura
Wataru Takahashi vs. Tatsuya So
Shoko Sato vs. Takuya Eizumi
Shintaro Ishiwatari vs. Kil Woo Lee