The 29-year-old Mongolian was ensured of his fifth title when Myogiryu lost an earlier bout.
Terunofuji loses for the first time in his debut at the sport’s highest rank.
At the halfway point, the new yokozuna is firmly in control and appears on his way to a 15-0 record.
The Mongolian outmuscles compatriot Ichinojo on the opening day of the Autumn Grand Sumo Tournament.
Fellow yokozuna Hakuho was forced to pull out over COVID-19 protocols.
Despite the loss, Terunofuji almost certain to be promoted to sumo's highest rank.