World number one and defending champion Lydia Ko had to settle for a 70 on Thursday, leaving her seven shots off the pace, while British Open victor Ariya Jutanugarn, who played alongside Chun, started with a disappointing 73.
South Korea's In Gee Chun and compatriot Sung Hyun Park were tied for the lead starting the second round of the Evian Championship in Evian-les-Bains in France, which got underway in calmer weather this morning.
Korean Park, a non-member of the LPGA Tour who led during this year's US Women's Open where she tied for third, grabbed a share of the lead by sinking a 6m birdie putt at the 18th.
Chun credited her commitment to her reads on the greens and her playing partners, Ariya Jutanugarn and Julia Engstrom for her strong play.
"I could see the putting lines and I was good rolling the ball on those lines", she said.
"It was tricky for me because on the back nine I really wasn't hitting fairways", Ko said. "I want to be happy on the course", she said.
"I feel like she's got the confidence where she feels like she can win every week, and that's a great position to be in", Ko said.
Canadian Henderson won her first major at the LPGA Championship in June, a win that she says "was a huge turning point in my life and my career". "Also the atmosphere is a little different, and of course the course setup is a bit more hard than what it is, so I'm the one that always really enjoys the challenge", said Ryu.
Ko heads in to the weekend nine strokes off the pace
"There's no benefit for just long hitters, " she said. Annie Park, joined by her mom and older sister, hit four landmarks in Paris on a whirlwind half-day tour."That was fun".
In-Gee Chun had to come from behind to win her first major title - but the South Korean golfer is leading from the front as she bids for her second this weekend.
This year, another young player emerged in her tournament debut.
Ko truly announced her arrival on the biggest stage as a 16-year-old when she finished second in Evian in 2013 - the year it became the fifth major in women's golf. "I know I'm good right now, my tee shot and everything is good right now, so just believe in myself and enjoy my golf".
Defending champion Lydia Ko opened with a one-under-par 70 and sits in a tie for 28th and seven shots back. I only started practising last week.
"I actually started to feel a little bit exhausted on the back nine".
Notable names to miss the cut at three-over include: Na Yeon Choi (WD), Mirim Lee (+10), Caroline Hedwall (+10), Karrie Webb (+8), Bronte Law (+8), Caroline Masson (+6), 2016 U.S. Open Champion Brittany Lang (+5), Juli Inkster (+4) and Morgan Pressel (+4).