He opened his studio in New York in 1968. Within a year Oku (1937 - 1993) held his first one-man show in Philadelphia and then exhibited widely throughout the United States, Holland, Germany, and Japan.In addtion, the Whitney Museum in New Yrok selected his work for the museum's highly acclamined 1970 exhibition, "Symbols and Images".

In 1970, Oku underwent an important artistic transition by discovering the adaptability of his work to the printmaking medium.Oku's unique style and expression account for his importance in the contemporary art movement. His figures are rendered in a deceptively naive, abbreviated manner producing compositions of superb patterns and two-dimensional design. The characters, in their frontal simpicity and silent expression recall the mystic qualities of Byzantine icons, while the bright vibrant colors and contemporary subject matter root his work firmly in the 20th century.

Oku's work is in the collections of Elton John, Charlie Watts, The Noyes Museum, Cincinnati Art Museum and Seiji Ozawa to name a few.