Known widely as the "King of Speed" before a bad accident 10 years ago while trying to break 300 km/h in an RX-7 FC, he was inspired to go back to street racing when he encountered the Devil Z, going as far as to get a new car, a highly tuned RX-7, from his oldest friend Kazuo Ota, a genius tuner who founded the Speed Factory RGO with Masaki long ago. He has a special fondness for rotary engines, and makes up for a lack of raw power with handling ability. Masaki VA in Wangan Midnight PS3 is Tokuyoshi Kawashima.
Masaki was skipped in the anime due to unknown reasons, but his car was briefly shown in Episode 21 of the anime. His RX-7 is similar to Keisuke Takahashi's from Initial D because they are both tuned and share the same color.