The event marked the promotion's fourth visit to Tokyo and first since
ONE: Century in October 2019. The event was originally host to Qatar, but moved to
ONE 166 on March 1. A flyweight kickboxing superfight between the
ONE Flyweight Muay Thai Champion Rodtang Jitmuangnon and former three-divisions
K-1 World Champion Takeru Segawa was expected to headline the event. This was mark the first time a non-title bout to be five rounds. However, Rodtang withdrew from the bout due to injury and was replaced by
Superlek Kiatmuu9 for the
ONE Flyweight Kickboxing World Championship bout. A
ONE Lightweight Submission Grappling World Championship rematch between current champion
Kade Ruotolo and
Tommy Langaker served as the co-main event. The pairing previously met at
ONE Fight Night 11 which Ruotolo retained the title by unanimous decision. A lightweight bout between former two-time
ONE Lightweight Champion Shinya Aoki and
Sage Northcutt was expected to take place at the event. == Results ==