The in-form Korean, who has won three titles this year, broke free from the chasing pack when he holed out from the 17thfairway for eagle at the Otone Country Club, West Course.
He leads on seven-under-par 203 as Japanese duo Yuta Ikeda and Satoshi Kodaira trailed in tied second place after shooting a 67 and 66 respectively at the Y150 million (approximately US$1.2 million) event sanctioned by the Asian Tour and Japan Golf Tour.
Scott Strange of Australia, who led on day one, was a further shot back in fourth place following a 67. Overnight leader Prayad Marksaeng of Thailand stayed in the title mix despite shooting a poor 72 to trail playing partner Kim by four shots.
Popular Japanese Ryo Ishikawa stayed in contention after posting a 68 to sit in tied eighth position alongside Richard T. Lee of Canada on a 208 total.
On a day where the lead changed hands several times, Kim made a late charge when his five iron approach shot from 198 yards found the back of the cup on the penultimate hole. A close range birdie on 18 earned him a two-shot cushion.
“I hit the ball really well. It was probably the best in three days. I struggled early in the round with my putter but I told myself to stay patient and I was rewarded with that eagle on the 17th hole,” Kim smiled.
“I didn’t see the ball go in. I heard the spectators shout and that’s when I knew it went in. It is nice to lead by two shots but anything can happen on this course. I need to be at least under par to have a chance to win,” he added.
Ikeda, a 13-time winner in Japan, stayed in the hunt for a second win in 2015 after shooting five birdies against three bogeys.
“You have to stay really patient on this golf course. If you can stay patient and keep the ball on the fairway then you will have a good chance to win. Kim is playing very well but I will only focus on my own game,” said Ikeda.
Prayad, a nine-time Asian Tour, struggled with a cold putter as he slipped to tied fifth place. He missed a six-foot par on the fifth hole and three putted on hole seven for bogey after making his only birdie on hole four.
“My game was good except for my putting. It was the same story like yesterday. I missed so many birdie chances and made some mistakes. Kim played very well and he deserves to take the lead but anything can happen on this course. If a few putts drop tomorrow, I might have a chance to win,” said the 49-year-old Prayad.
Scores after round 3 of the Asia Pacific Open Mitsubishi Diamond Cup being played at the par 70, 7101 Yards Otone CC course (am – denotes amateur):
203 – K.T. KIM (KOR) 67-69-67.
205 – Satoshi KODAIRA (JPN) 71-68-66, Yuta IKEDA (JPN) 68-70-67.
206 – Scott STRANGE (AUS) 64-74-68.
207 – Yuki INAMORI (JPN) 73-65-69, Toshinori MUTO (JPN) 69-68-70, Prayad MARKSAENG (THA) 67-68-72.
208 – Yusaku MIYAZATO (JPN) 70-70-68, Ryo ISHIKAWA (JPN) 69-71-68, Richard T. LEE (CAN) 66-74-68, Shugo IMAHIRA (JPN) 70-68-70.
209 – Tadahiro TAKAYAMA (JPN) 72-71-66, Scott BARR (AUS) 70-71-68, Lionel WEBER (FRA) 69-71-69, Keiichiro FUKABORI (JPN) 68-72-69, Tomohiro KONDO (JPN) 68-72-69, Daisuke KATAOKA (JPN) 69-70-70.
210 – Mardan MAMAT (SIN) 73-70-67, Younghan SONG (KOR) 71-70-69, Michio MATSUMURA (JPN) 70-71-69, Lucas HERBERT (am, AUS) 71-69-70, Hiroyuki FUJITA (JPN) 71-69-70, Atomu SHIGENAGA (JPN) 70-70-70, Tetsuji HIRATSUKA (JPN) 74-66-70, Shunsuke SONODA (JPN) 70-67-73, Hyungsung KIM (KOR) 68-69-73, Hideto TANIHARA (JPN) 69-68-73.