Sômai has been fascinated by film since he was a child and made his first film in high school. He first worked as assistant director in Nikkatsu studio and in 1975 became an independent director. He made his directing debut with the film Tonda kappuru (Tonda Couple, 1980), and afterwards made Gyoei no mure (1983), Taifu Club (Typhoon Club, 1985), Hikaru onna (1987), Tôkyô yôkű irasshaimase (Tokyo Heaven, 1990), Ohikkoshi (Moving, 1993), An haru (Wait and See, 1998) and Kaza-hana (2001). Kinema Junpo, a prestige Japanese film magazine, proclaimed him the best Japanese director of the 1980s.