Coming onto the final hole with a one-stroke lead over Japan's Mitsuhiro Tateyama, Clarke watched Tateyama's shot for an eagle from out of the green nudge the edge of the cup to go left.
Then it was Clarke's turn for an eagle attempt and he calmly sank a 12-metre putt to finish off the contest.
Clarke ended the day with one eagle, four birdies against two bogeys for a 68 and a four-round total of 18-under 270 to receive the winner's check of 30 million yen (US$254,000).
“I was trying to putt as close as I could and fortunately it went in, but Tateyama played fantastic all day,” Clarke said of his eagle putt.
“It's the first time in my life to defend a title. I'm very pleased to do it here on one of my favourite golf courses. I love this golf course. It's one of the best conditions, best greens to putt.”
Tateyama, who eventually birdied the final hole, carded six birdies against one bogey to finish second at 272, followed by fellow Japanese overnight co-leader Hideki Kase third at 274.
golf