Honda youngster Toshiki Oyu set the pace on the opening day of Super Formula's second pre-season test at Fuji Speedway, outpacing the rest of the field by more than three tenths of a second.
Oyu, who is going into his second season driving for Nakajima Racing, left it until the dying minutes of the day's running to post his best time, a 1m27.371s, knocking fellow Honda man Nirei Fukuzumi off the top spot.
Having topped last December's post-season test at Fuji, Dandelion Racing driver Fukuzumi was the driver to beat for most of the two-hour afternoon session, establishing himself at the head of the times with a 1m21.808s with a little under an hour left on the clock.
After a late red flag, caused by Tatiana Calderon coming to a stop exiting Turn 10, Fukuzumi improved further to a 1m21.722s, only to see that time blitzed to the tune of 0.351s by Oyu as the chequered flag fell.
Impul Toyota driver Hirakawa topped the earlier morning session with a 1m21.844s, and that effort stood as the third-quickest of the day as the 2020 series runner-up didn't improve in the afternoon.
Ritomo Miyata was another late improver in the 10-minute shootout that followed the day's third and final red flag, and ended up fourth-fastest and the top rookie in the best of the TOM'S cars.
Last year's Fuji polesitter Tomoki Nojiri was fifth for Team Mugen, followed by Ukyo Sasahara, who continues to substitute for the recovering Tadasuke Makino at Dandelion.
Kazuki Nakajima returned to Super Formula action at Fuji after having to miss the Suzuka test as he quarantined on his way back from a Toyota hypercar test at Paul Ricard, and was seventh-fastest for TOM'S.
After a low-key first pre-season test of the winter at Suzuka, Naoki Yamamoto continued to lag behind the pace of Nakajima teammate Oyu as he ended up eighth-fastest, just under ninth tenths off the pace.
Hiroki Otsu (Mugen) and Sena Sakaguchi (Inging) made it two more rookies inside in the top 10 ahead of Kamui Kobayashi's KCMG stand-in Kazuko Kotaka.
Yuhi Sekiguchi (Impul) endured an eventful day as he caused two red flags, one in each session, on both occasions appearing to spin shortly after exiting the pits. He ended the day 12th-fastest.
Yuichi Nakayama continues to fill in for the absent Sacha Fenestraz at Kondo Racing and was 17th-fastest, ahead of Calderon (Drago Corse), whose stoppage was the result of a gear selection issue.
Testing continues with two more two-hour sessions planned for Wednesday.