Kai Kogashiwa

Kai Kogashiwa (小柏 カイ Kogashiwa Kai) is a street racer from Tochigi prefecture, and a son to a legendary downhill ace and Bunta Fujiwara's rival, Ken Kogashiwa. He is originally seen driving his father's Toyota MR2, then later on in his Toyota MR-S as a Project D opponent.

Past
Ken taught Kai in the racing world from a young age, participating in karting competitions which made him specialized in midships (colloquial term for mid engine, rear drive). Before his transition to street racing, Kai was the fastest motorcyclist on Irohazaka. It can be seen that Kai's specialty on Irohazaka is similar to Takumi on Akina as he lives at Lake Chuzenji (which is at the top of Irohazaka) and takes the road during his daily commute to the bottom.

New Eight-Six
Kai had challenged Takumi on the Emperor's home course of Irohazaka. Prior to challenging Takumi, he had a quick encounter with Bunta Fujiwara driving the AE86 when Bunta passes Kai on the opposite lane on a hairpin, barely missing his car. Kai had defeated Seiji Iwaki of Emperor and wanted to defeat Kyoichi Sudo as well, but set his sights on Takumi after Sudo's defeat. During their battle, Kai gives Takumi the lead, and keeps up with him until the 33rd corner, in which Kai uses a trick taught to him by his father to overtake Takumi by jumping a turn in a break in the guard rail. This gives Kai the lead, shocking Takumi. However he had used the move rather too early, as said by Kyoichi because the opponent can recover from it psychologically and they can analyze the move. As Kai jumps on the next hairpin, Takumi follows his suite, making Kai surprised. Despite this, Kai proclaims that he'll still keep his pace and that he'll not be stopped. However Takumi comes side by side to him near the final corner on the final bridge, as they both jump in the air, Kai spins out after his car loses traction from landing on leaves on the side of the road and was defeated. He later on thanks Takumi for not hitting his father's car.

Kanagawa Expedition
Kai reappears as an opponent for Project D in Kanagawa prefecture, this time with his modified Toyota MR-S as he battles Takumi once again at Nagao pass. Kai represents the downhill ace for R.T. Katagiri along with Hideo Minagawa as the uphill ace. During their battle Kai takes the chasing position and notes the changes and upgrades in Takumi's Eighty-Six. He also notes the improvement in Takumi's skills and driving techniques as he witnesses Takumi doing the wheel lift gutter technique in front of him, but he manages to keep up with him. As the battle goes on, Kai notes that Takumi was pulling away from him slowly, which makes him abandon his circuit racing style driving and to go full out to catch up to Takumi. He later on closes the gap on the entry of a sharp corner, showing off his superior braking skills. On the next corners while approaching the final stretch, Kai tries his best to keep up with Takumi, but Takumi pulls away from him, causing Kai to strain and put too much pressure on his car, which caused his MR-S to snap oversteer and spin out, losing the battle once again. After the battle, he congratulates Takumi and says he should go on street racing as he shows extraordinary skills in it.

Later on Kai and Hideo Minagawa along with other teams spectates Project D's final battle against Sidewinder at Tsubaki Line.

Trivia

 * Kai appeared in MF Ghost as Ryosuke Takahashi's friend. They don't want Kai to disclose information about themselves. He also appeared as guest commentary in MFG opening race.
 * In Battle Stage, after overtaking Takumi using the "Irohazaka Jump" in the 33rd corner, he states that he'll have no chance at passing him, while in the original version, he explains about the meaning of the corner, and how it is the "reckless driving of locals". However, in Battle Stage, he still proclaims that he's "won the battle".
 * In the manga, Kai jumped two times before Takumi emulated the move. In Third Stage, Kai does it thrice before Takumi does too.
 * In the Arcade Stage games, he is known to use the "Irohazaka Jump" in the 33rd corner to beat the player. Because of this, the player must emulate that move in order to defeat Kai, as he is known to be a hard opponent in the game.