One of the first racers from Saitama to actually race against Takumi with his turbocharged Levin, he appeared later in Fourth Stage, this time replacing the turbocharger with a supercharger for more linear acceleration. Wataru is a skilled driver who honed his skills on the treacherous Shomaru Pass. He came to Gunma in hopes of facing new racers to challenge. As well as to watch over his sister Kazumi, who just got a job at a hotel with her aunt. Wataru reappeared in episode 9 of Fourth Stage as Nobuhiko's cousin, to watch Takumi race against the Northern Saitama Alliance in the hopes of finding a weak spot.

Wataru later raced against Keisuke Takahashi in a wet weather race, but when his tires lost grip upon touching a metal gutter while he adjusted his wipers, he was defeated.

Some time later, Wataru confronts the imposter Project D somewhere in Saitama and helps the real Project D expose them as the frauds they are.