Kei Tsukasa is the primary pen name of Ryou Kurashina (real name Keiji Ooba), a Japanese manga artist and original creator born on June 23, 1950 in the city of Kuroiso, now known as Nasushiobara, in Tochigi Prefecture. He made his debut as a manga artist in 1971 working for the magazine Manga Goraku. In the early part of his career, he focused on creating works for youth and adult-oriented magazines, often writing stories centered on gambling and the nighttime entertainment business, a genre he would later help pioneer.

During the 1970s and 1980s, Tsukasa created a wide range of manga series covering various genres including action, drama, and sports such as boxing, judo, and rugby. Notable series from this period include Aizu Otoko Uta, Takeda Miken Hoshi, and Shouwa Bankara-ha. One of his major successes from this era is Yabou no Mure (Ambition Herd), a long-running series that was collected in 28 volumes. His work from this period contributed to his credit as the original creator for the 1990 OVA Kentoshi, for which he is listed as providing the original work.

Feeling a sense of creative stagnation as a manga artist, he decided to abandon drawing and restart his career as a full-time original creator under a new name. Changing his pen name to Ryou Kurashina, he began writing the stories for manga rather than illustrating them. This transition marked a significant turn in his career, as his original works were frequently adapted into television dramas. His most famous creations under the Kurashina name include the popular series Jotei, Jouou, and Yaou, all of which became live-action TV dramas. Many of these stories focus on female protagonists navigating the nightlife and entertainment districts of Japan, a subgenre known as neon-gekiga which he is credited with founding.

Throughout his career, he has also operated under the real name Keiji Ooba, running the editorial production companies Free Hand and Office Kei, which were contracted by publishers to produce entire magazines or sections of them. With a career spanning from the early 1970s to the present, Kei Tsukasa, also known as Ryou Kurashina, is recognized as a significant and pioneering figure in gekiga, particularly for his influential work in establishing the neon-gekiga genre. More than forty of his works have been published in tankobon format.