Shunya Takeyasu birdied the final hole to open his campaign at the Fujisankei Classic with a four-under-par 66, taking a one-shot advantage over the chasing pack where five players are tied for second place at the Fujizakura Country Club on Thursday.
Takeyasu's scorecard featured seven birdies and three bogeys- giving him his first-ever lead after a round since he first competed on the JGTO in 2015.
JGTO money list leader Keita Nakajima, meanwhile, had a strong start to the tournament, carding five birdies and two bogeys to finish the day with a score of 68.
This places him in a tie for second alongside past champions Park Sang-hyun of South Korea (2019 winner), Hiroshi Iwata (2014 winner), Naoyuki Kataoka and surprise amateur contender Rintaro Nakano.
Australia's Brad Kennedy, 2021 winner Shugo Imahira, two-time champion Ryo Ishikawa, and Takumi Kanaya were among the seven players tied for seventh, just one shot further back.
Takeyasu was delighted with how he dealt with the challenging course.
"I'm extremely happy, to say the least. This is the kind of course where I would be satisfied just to play at even par, so four-under feels like a score I might not achieve even if I played 100 times!" said Takeyasu.
The good start has whetted Takeyasu's appetite to pursue his JGTO breakthrough.
"I can't help but think about it. But I'm aiming to not dwell on it too much. I'll give it my all starting tomorrow," said Takeyasu, whose best Tour finish to date was a tied-fifth at the 2018 Japan Open.
Nakajima has vowed to improve his driving accuracy and hit more fairways.
"It's the kind of course where if you're constantly in the rough, you're constantly bogeying," he said.
"So, first and foremost, I want to get the ball on the fairway, just like today. With a solid start right now, it would be fantastic if I could extend my score."
Leading first round scores:
66: Shunya Takeyasu;
67: Rintaro Nakano (am), Keita Nakajima, Naoyuki Kataoka, Hiroshi Iwata, Park Sang-hyun (Kor);
68: Shugo Imahira, Takumi Kanaya, Brad Kennedy (Aus), Hirotaro Naito, Taisei Yamada, Ryo Ishikawa, Taichi Nabetani;
69: Yuto Katsuragawa, Keisuke Ozaki, Kensei Hirata, Satoshi Kodaira.