After graduating from Tokyo Metropolitan North High School, he attended Hosei University.
After graduating from high school, he took a position at Toshiba while studying in the department of literature at Hosei University.
Dezaki resigned after working for seven years at Toshiba, leaving Hosei University in the middle of a term as well.
In 1969, Dezaki became a freelancer, directing and writing screenplays for series and films produced by Tokyo Movie Shinsha, Tatsunoko Production, and Sunrise.
In 1977, he founded Magic Bus and produced and animated Shin Kyojin no Hoshi.