| Age | 15 |
| Sex | Male |
| Car | Toyota Sprinter Trueno 2door GT-APEX (AE86) |
| Plate | 12-186, classification 57 |
| Year | 1986 (Kouki) |
| Color | High-Tech Two-Tone |
| Custom Parts | Toyota OEM Rear Spoiler, TRD Sports Muffler, RS Watanabe Eight-Spoke F8 wheels, Cusco 7-Point Bolt-On Roll Bar, OEM AE101 Throttle Bodies, Black Valve Cover, TODA Cams (272/272), TRD 0.8mm Gasket, TODA Cam Pulleys, TODA Air Intake, Tomei Pistons, TODA Conn. Rods, TODA Header, FREEDOM ECU, TODA Timing Belt, TRD Plug Wires, TODA Valves, OEM AE111 Forged Crankshaft, & AE92 Kouki Redtop Block. |
| Voiced by | Atsushi Abe |
Shinji Inui (乾 信司 Inui Shinji) makes his debut during Project D's battle against Team Spiral. Shinji is a member of Sidewinder and therefore second driver of this team. Shinji appears to be a boy (possibly younger than Takumi) but seems very intelligent. Shinji's car is the notchback coupe variant of the AE86 Trueno (not to be confused with Takumi's Eight-Six). He is the fourth character to drive a Toyota AE86 model, after the fake Takumi's Trueno AE86.
In the end of the final episode of final stage, it is unknown who won the race when he races Takumi's AE86. In the final chapters of the manga (and the Final Stage anime), Shinji lost to Takumi, due to both cars spinning out. With the tires of Takumi's 86 locking up, it sent Takumi's 86 into a spin. Shinji had no choice but to follow. At this moment, with the experience gained from the engine blow in Akagi when going against the Evo III, Takumi instinctively presses on the clutch, freeing up the tires and regained control of the 86 momentarily. However, Takumi is now going in reverse with inertia alone. Shinji, on the other hand, lacks actual dogfight experience and did not know what to do, spinning a full 360 degree, causing him to lose more momentum than Takumi did. Takumi won by crossing the finish line backwards with his 86. Shinji's 86 ended up facing the finish line after the 360 spin.
The reason the winner is disputed is because of Kyoichi Sudo's quote from second stage, where he says a blown engine means defeat. Therefore, Takumi technically lost when he blew his engine in the final corner, but so did Shinji as Takumi still crossed the line. Takumi is however seen as the winner, although as stated previously the actual winner is unknown.
Shinji later apologized to his mother and his boss, Go Hojo, for losing the race; however neither of them were angry, and Go said that Shinji at least gave it his all.
Eiji Kubo learns that Shinji has incredible spatial intelligence after hearing his mother's story about Shinji having high IQ but not having good grades and Shinji's penchant of doing nothing but staring at the roadside when he was still a little boy, explaining why he has such excellent knowledge of the track.
