He was expected to inherit his family's seafood wholesale business, Hotei Tora (布袋寅), in Tsukiji, becoming the sixth generation owner, but instead chose to become a race car driver.

Upon returning from the UK without sufficient funds, he borrowed money from his grandfather, Kazuyori Mutoh (武藤和順), the fourth-generation owner of Hotei Tora, after writing an IOU.

He achieved his first Super GT victory in the final round at Fuji Speedway, starting from pole position.

Mutoh captured his first win in Liberty Challenge Race 1 at the Indianapolis Motor Speedway road course on United States Grand Prix weekend, starting from pole position.

He went on to win another race at Kentucky Speedway and finished second in the championship standings, earning Rookie of the Year honors.

[1]Mutoh made his debut for Andretti Green Racing at Homestead-Miami Speedway in March and in May was the highest qualifying rookie for the 2008 Indianapolis 500, starting from 9th.

He failed to finish higher than 6th in the remainder of the season, but beat transitional driver Justin Wilson to the Rookie of the Year title and 10th place overall in the series.

However, on a restart with 14 laps remaining, Mutoh, running fifth, made contact with Takuma Sato, who was in sixth, resulting in both drivers retiring.

At the Indianapolis 500, he qualified ninth, matching his 2008 effort, but retired from the race due to handling issues.

Mutoh has been announced as an Aguri Suzuki Honda driver in the Super GT series in Japan for 2011, alongside Takashi Kobayashi.