Kai Kogashiwa

Kai Kogashiwa (小柏 カイ Kogashiwa Kai) (Caine in Sega adaptation) is a street racer from Tochigi prefecture, and the son of Ken Kogashiwa. He was a go-kart driver in his youth, later having a brief stint as a street racer (originally on motorcycles, and then later cars) before becoming a professional racer and joining Katagiri. He originally drove his father's Toyota MR2, before getting his own Toyota MR-S when he became a professional.

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 Arc
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 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, surprising Kai. 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 is horrified, for there is a patch of leaves where his car would land. Landing on the leaves, he quickly loses control of the car, causing it to spin out. Takumi misses Kai by mere inches, speeding off before coming to a stop ahead. Kai 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 skill in it.

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

MF Ghost
Kai appeared in MF Ghost as a friend of Ryo Takahashi. They don't want Kai to disclose information about himself. He also appeared as guest commentary in MFG opening race.

Trivia

 * In the Arcade Stage games, Kai will often recreate his famous Irohazaka jump when racing the player.