When he failed the college entrance exams, he read a specialized magazine that his younger sister had bought, Scenario, which led him to enroll in a screenplay institute with the funds he had saved up to go to prep school.

He got recognized for the screenplays he had written there, and in 1969, at the age of 19, he made his debut as a scriptwriter in the 45th episode of the TV historical drama Ōedo Sōsamō.

However, he got tired of fixing scripts that he did not agree with and stopped writing altogether, claiming he got fed up with penning human drama pieces, so he spent the rest of his time working as a salesman for educational equipment and various ceremonial occasions, while at the same time helping out with shōjo manga original stories and plots for TV dramas without taking credit for any of his work.

Later, he roamed Europe with the money he had saved from his salesman job, and when he returned to Japan after running out, with the help of his acquaintance, screenwriter Fukiko Miyauchi, he returned to work as a scriptwriter in 1976 for an episode from Manga Sekai Mukashi Banashi, an anime TV series produced by Dax International.

Before, during and after Lugia's creation, Shudo would heavily consume alcohol and tranquilizers, which he claimed cleared his mind when working, and it contributed to his failing health.