He debuted in 1955 and prolifically wrote horror comics for paperback books for rental. After focusing on magazines, he wrote "Snake Girl," the final story of a trilogy named "Reptilia" in the weekly magazine Shojo Friend, published in 1966. Umezu firmly established his reputation as a horror manga artist with the work. After creating "Orochi" in 1969, he started writing "The Drifting Classroom" in a weekly comic magazine in 1972. In the story, children travel into the ruined future world, where they overcome many difficulties. He received the publisher's award "Shogakukan manga-sho" for "The Drifting Classroom" and other manga in 1975. In 1976, he started writing a comedy manga "Makoto-chan" featuring a kindergartener for a weekly magazine. The main character's trademark pose, which sounds like "Guashi," and his way of talking, which adds "nanora" at the end of sentences, became popular. After that, he went on to write "My Name Is Shingo," "God's Left Hand, Devil's Right Hand," and "Fourteen," among other manga. After completing "Fourteen" in 1995, he suspended his work because of acute tendonitis he developed over the years.