Muto had nine birdies – including five on the front nine – against a lone bogey on the final hole to finish at 12-under 201 and claim his first title in two years.
“It’s been a while since I won and I never thought I would break the drought in such a big tournament,” Muto said. “Too bad about the bogey on the last hole but Other than that I was very pleased with my round.”
Fernandez-Castano, who won the Singapore Open on Monday, saw his chances for a comeback dashed with a bogey on 17 and finished at 8-under 205 after a 71.
Australian Brendan Jones had an eagle on the par-5 18th to complete a 68 that left him in fifth place.
The $2.5 million event was shortened to 54 holes after the Saturday’s third round was washed out by rain.