Considered an auteur of Japanese animation by film and television critics, Watanabe's work is characterized by evocative uses of music, mature themes, and the incorporation of multiple genres.

His next directorial effort was the critically acclaimed 2004 anime series Samurai Champloo which began broadcasting on Fuji Television in Japan on May 19, 2004.

[1] In recent years, he has been active as a creative music producer, overseeing the 2004 film Mind Game, 2008's Michiko & Hatchin, and supervising the storyboards for episode 12 of Tetsuwan Birdy: Decode.

In 2012, he directed the anime series Kids on the Slope (Japanese title: Sakamichi no Apollon), a coming-of-age story about young jazz musicians, which premiered in April 2012 on Fuji TV's Noitamina block.

[2] In 2009, it was announced that Watanabe would be working as an associate producer on the upcoming live-action adaptation of Cowboy Bebop, alongside his fellow Sunrise staff members Kenji Uchida and Keiko Nobumoto.