Having scored three bonus points for pole position in qualifying earlier on Saturday, Nojiri only needed a top-three result to become Super Formula's first back-to-back champion since Tsugio Matsuda in 2008.
But the 33-year-old wrapped up the championship in style with a strong run to second, as his chief championship rivals Sacha Fenestraz and Ryo Hirakawa could manage no better than 16th and ninth respectively.
His result, combined with a second victory of the season for Sasahara, also helped Mugen clinch the teams' title with Sunday's finale still to run.
Story of the race
Nojiri led the way from pole initially ahead of Toshiki Oyu and Sasahara, as Ritomo Miyata slipped to fourth with a comparatively poor start from second on the grid.
But the man on the move was Sasahara, who dispatched the Nakajima Racing machine of Oyu for second place at the start of lap four at Turn 1 before piling the pressure on his team-mate Nojiri.
When the pitlane window opened on lap 10, Sasahara was first to head in for a fresh set of Yokohama tyres, with Nojiri responding next time round.
Nojiri initially emerged ahead but on colder tyres he was rapidly reeled in by Sasahara through the first sector, and didn't get in the way of his team-mate when he launched an attack heading into the hairpin.
Once in the lead, Sasahara was never threatened again, building an advantage of 12 seconds en route to his second win of the season and of his career.
After both the Mugen cars stopped, TOM'S driver Miyata assumed the lead of the race and looked in a strong position to challenge for the final spot on the podium before he pitted on lap 25.
But a slow stop for Miyata left him down the order, opening the door for Red Bull junior Ren Sato to grab his first podium of his rookie season.
Leaving his pitstop until lap 19, Sato was able to pick off Tadasuke Makino, Yuhi Sekiguchi and finally Oyu to take third and boost his chances of keeping a place on Honda's roster in 2023.
Oyu had to be content with fourth place, while Miyata fought his way back ahead of Impul driver Sekiguchi to finish fifth.
Makino was seventh in the best of the Dandelion cars, while the remaining points went to Sho Tsuboi (Inging), Hirakawa (Impul) - unable to make serious progress from 11th despite leaving his pitstop until lap 27 - and Sena Sakaguchi (Inging).
Like Hirakawa, Kondo Racing's Fenestraz failed to make progress at the start and endured a miserable race that yielded a lowly 16th place.
As a result, Hirakawa and Fenestraz go into Sunday's finale level on points in the battle for second in the drivers' standings.
Race results:
| Cla | # | Driver | Team | Gap |
|---|---|---|---|---|
| 1 | 15 |  Ukyo Sasahara |
Team Mugen | |
| 2 | 1 | Tomoki Nojiri |
Team Mugen | 12.589 |
| 3 | 53 | Ren Sato |
Team Goh | 14.212 |
| 4 | 65 | Toshiki Oyu |
TCS Nakajima Racing | 19.638 |
| 5 | 37 | Ritomo Miyata |
Kuo VANTELIN TEAM TOM’S | 19.995 |
| 6 | 19 | Yuhi Sekiguchi |
Team Impul | 21.206 |
| 7 | 5 | Tadasuke Makino |
Dandelion Racing |
23.151 |
| 8 | 38 | Sho Tsuboi |
P.MU/CERUMO･INGING | 25.941 |
| 9 | 20 | Ryo Hirakawa |
Team Impul | 26.423 |
| 10 | 39 | Sena Sakaguchi |
P.MU/CERUMO･INGING | 27.631 |
| 11 | 64 | Naoki Yamamoto |
TCS Nakajima Racing | 29.535 |
| 12 | 55 | Atsushi Miyake |
Team Goh | 33.444 |
| 13 | 6 | Hiroki Otsu |
Dandelion Racing |
35.643 |
| 14 | 3 | Kenta Yamashita |
Kondo Racing | 42.243 |
| 15 | 12 | Nirei Fukuzumi |
ThreeBond Drago CORSE | 44.485 |
| 16 | 4 |  Sacha Fenestraz |
Kondo Racing | 44.851 |
| 17 | 50 | Nobuharu Matsushita |
B-Max Racing Team | 46.689 |
| 18 | 7 | Kamui Kobayashi |
KCMG | 48.700 |
| 19 | 14 | Kazuya Oshima |
docomo business ROOKIE | 55.137 |
| 20 | 18 | Yuji Kunimoto |
KCMG | 57.781 |
| 21 | 36 | Giuliano Alesi |
Kuo VANTELIN TEAM TOM’S | 58.552 |
| View full results | ||||
