Veteran golfer Hideki Matsuyama rallied to win the PGA Tour event, carding a 9-under 62 in the final round and achieving victory without back pain.
Mikumu Horikawa is one shot off the pace at the ZOZO Championship, while 2021 Masters champion Hideki Matsuyama struggled in his opening round.
The local favorite made up for missing out at the inaugural tournament and the Olympics with a clutch performance on home soil.
Runner-up Mone Inami wins a playoff with Lydia Ko to capture Japan's first medal in Olympic golf.
Masters champion Matsuyama stayed in contention but missed clutch putts down the stretch.