Kazuo is the grandmaster of Japanese horror manga. He published his first manga while still at high school and began working professionaly in the field after his graduation. His first creations were 'Betsu-Sekai' ('Another World') and 'Mori-no-Kyoudai' ('The Brother and Sister in a Forest'). He mainly created his works for so-called Kashi-hon, magazines that were not for sale but for rent. He developed his detailed horror style in 1962, when he settled in Tokyo. His works 'Kuchi ga Mimi made Sake-ru Toki' ('The Moment The Mouth Tears to Ears'), 'Hebi Shoujo' ('The Snake Girl') and 'Hito-kobu Shoujo' ('A Girl Who Has A Human-faced Lump on Her Cheek') were his first claims to fame as a master in the horror genre.
He was also a pioneer in "Rabu-kome" (romantic comedies), starting with his story 'Romansu-no-Kusuri' ('The Magical Medicine for Romance'). His award-winning work 'Hyouryu Kyoushitsu' ('The Drifting Classroom') was serialized in the weekly magazine Shounen Sunday from 1972 to 1974. He then came up with the slapstick comedy 'Makoto-chan' in 1976. Ever since, Umezu has released many other outstanding comic works such as 'Neko-me Kozou' ('The Cat-eyed Boy'), 'Orochi', 'Iara', 'Senrei' ('Baptism of Blood'), 'Watashi ha Shingo' ('My Name is Shingo'), 'Kami no Hidari-te Akuma no Migi-te' ('God's Left Hand, Devil's Right Hand') and 'Fourteen' . Some stories were made into movies, TV drama series and other media products.