Hideki Matsuyama, making his first JGTO start in four years, took the lead after firing a flawless eight-under-par 63 in the first round of the Dunlop Phoenix Tournament in Miyazaki on Thursday.
The 2021 Masters champion holds a one-shot advantage over 22-year-old amateur Yuta Sugiura, who claimed solo second place and stole the spotlight.
Finishing one shot behind at 65 was the current top-ranked money leader, Keita Nakajima, along with South Africa's Shaun Norris and Yusaku Miyazato.
Kazuki Higa began his title defence with a modest 70, securing a share of 29th place. Meanwhile, PGA Tour heavyweights Wyndham Clark and Brooks Koepka, headlining the 84-man field this week, struggled to 71 and 73, respectively, leaving them tied for 49th and 66th.
As a source of national pride in golf, Matsuyama didn't disappoint the fans who gathered at the Phoenix Golf Club to witness his rare homecoming.
Starting from the 10th tee, Matsuyama made a strong beginning with birdies on the 11th and 15th before recording an eagle on the par-five 18th, turning in at four-under.
Maintaining momentum, he notched two consecutive birdies on the first and second holes before making additional gains on four and seven, positioning himself to potentially reclaim the title he last won in 2014.
This strong effort put a smile on Matsuyama's face, marking his first competitive start since the PGA Tours' ZOZO Championship in Chiba, where he finished a disappointing tied-51st.
"I believe it went well," said Matsuyama when asked to assess his flawless round. "I was worried and anxious before the start, but I made some good shots, and I didn't make any big mistakes with my putts. I'm glad I got off to a good start. I aim to improve as the days go by and secure a favourable position for the final day."
The highlight of Matsuyama's round came on the 18th when he hit his "fluke" iron shot to about 1.5 meters from the pin. "I got lucky there; it rolled in and ended up close. I was pleased as the eagle helped me to extend my score," he said.
While Matsuyama enjoyed his opening round, the same cannot be said for his playing partners and fellow major winners Clark and Koepka.
Koepka, a five-time major winner and two-time winner in this tournament, endured a tough day. Even an eagle and three birdies were hardly enough to make up for seven bogeys conceded.
"Unfortunately, I couldn't play well myself, but I still enjoyed it (playing alongside Matsuyama)," said Koepka.
"I aim to minimise mistakes as much as possible. I made some simple mistakes today, so if I can reduce those, I think I can play comfortably."
Clark, this year's US Open champion, also endured a roller-coaster round, trading four birdies with as many bogeys.
"I didn't have a particularly good performance today. Both my tee shots and putts didn't go well throughout the day. However, I finished even par, so I think I could build on that for tomorrow," said Clark.
"I want to improve the accuracy of my tee shots and adjust to make the putts that I couldn't make today. I aim to be able to sink putts more effectively tomorrow."
Leading first round scores:
63: Hideki Matsuyama;
64: Yuta Sugiura (am);
65: Yusaku Miyazato, Shaun Norris, Keita Nakajima;
66: Yuwa Kosaihira, Song Young-han (Kor), Scott Vincent (Zim);
67: Yujiro Ohori, Taihei Sato, Daijiro Izumida, Yuta Kinoshita, Taiki Yoshida.