Shinji Inui is the downhill driver for Sidewinder. Shinji appears to be a boy (possibly younger than Takumi) but seems very intelligent. Shinji has many parallels to Takumi, in that he has next to no interest in racing and that he had been driving years before he had his license.
Shinji's car is the notchback coupe variant of the AE86 Trueno (not to be confused with Takumi's Eight-Six), which belonged to his deceased father.
He is the third character to drive a Toyota AE86 model, after Wataru's Levin AE86.

(Source: Wikipedia, Initial D Wiki)