Keiichiro Aizawa is the character who drives the silver Toyota Supra RZ dubbed as the "Monster Machine" tuned by Kou Tominaga, Kazuo Ota, Kazuhiko Yamamoto and Akio Asakura. After meeting Devil Z, Kei decided to chase after him. His desire for racing and his car choice was inspired by his father, who drove a MkII Supra and was killed by a drunk driver. He works in a host club to finance his racing activities. After he lost the race against the Devil Z and Blackbird, the tuners detuned his 800HP engine to 400HP and repainted his Supra to the same Silver as his father's.