Osamu Tezuka's "Metropolis" made a deep impression on Yokoyama who wished to become a manga artist in earnest and so he contributed his works to a comic book in his high school days.
He found a new job as a publicity department member for a movie company based in Kobe and pursued his manga artist career on his free time.
Yokoyama came out with the first book White Lily Story (白百合物語, Shirayuri monogatari) for his manga artist debut, which caught Osamu Tezuka's attention.
Making good use of his vast exposure to movies during his previous job, he produced consecutive popular hits in various genres, both in comics and anime, such as Iga no Kagemaru, Akakage, Sally the Witch, Giant Robo, Babel II and so on.
With the writing of Suikoden (水滸伝, Water Margin) (1967–1971) and Sangokushi (1971–1987), he began a new chapter in his career as he drew mostly comics based on original stories with material from China's and Japan's histories.
[11] Araki also said that Jotaro Kujo wearing his school uniform in the desert has its roots in Yokoyama's Babel II, and that if he were to draw Stardust Crusaders over again, he would base the Stands on Tetsujin 28-go.