Born in 1966, Watanabe joined Studio Mates in 1986 and debuted his first original picture with the same studio. In 1988 he moved to Shinei Videos and was active in a wide range of roles including key animator, animation director, and director.
Watanabe directed the short theatrical release Obachan no Omoide (2000), and the feature film Doraemon: Nobita’s Dragon 2006 (2006) and became a free agent in 2011. After that time, he tirelessly built up his directing portfolio with projects such as the TV series Mysterious Girlfriend X (2012), Danchi Tomoo (2012-15), If Her Flag Breaks (2014), Space Brothers (2012-14), and Ace Attorney (2016). Three TV series directed by Watanabe aired in 2018, including After the Rain, Gurazeni, and Major 2nd.
Children of the Sea is his fourth time directing a full-length theatrical release.