The Spaniard has won six of his 14 European Tour titles in his home country, including the Valderrama Masters in 2011 and 2017.
The Englishman has not won a tournament since his shock 2016 success at Augusta National, but was joint second with a three-under 69 in the first round of the US$9.5 million US PGA tournament.
There was just one hiccup -- none of the top five, or even the top 10, was from China.
Sweden's Alexander Bjork was second while Australian Lucas Herbert and England's Jordan Smith came third.
Chun, ranked 27th in the world, finished 16 under par 272 to claim the US$300,000 first prize at the LPGA KEB Hana Bank Championships.
Disabled golfer Dennis Walters and the late Peggy Kirk Bell, an LPGA charter member, will also be enshrined in ceremonies on June 10 at Pebble Beach ahead of next year's US Open, raising total membership in the Hall to 160.
Molinari and Fleetwood became the first European pair to win all four of their matches together at Le Golf National in France.
Koepka, who missed nearly four months in early 2018 with a left wrist injury, also managed four other top-10 efforts in the season, including second-place finishes at the WGC HSBC Champions and at Colonial.
Brandt Snedeker started the day with a three-shot lead and led by five with 11 remaining in regulation before falling by the wayside.
American Kevin Tway was alone in second after a bogey-free four-under 68.
Defending champion Tyrrell Hatton, seeking a third straight win in the tournament, carded a two-under to sit alongside reigning US Open and US PGA champion Brooks Koepka.
Lai Yiyan has won so many tournaments that she has lost count. She is nine.
Frenchwoman Corine Remande, 49, said she was taking legal action against the event's organisers after being hit on Friday's opening day.
The USA were thrashed 17.5 to 10.5 on Sunday, ensuring that the long wait for an American victory on European soil would continue.
His miserable Ryder Cup record now stands at 13 wins, 21 losses and three halves.