Watanabe's technique is derived from Japanese Folk tradition. He was one of a small group of artists who, in the 1930s, devoted themselves to keeping alive various traditional arts, including stencils, as part of a broad Japanese Folk Art Movement. His stencils, while based on biblical themes have little, if any, Western influence in the art. Expressionless, long faces, are typical of his human figures.

Watanabe became a Christian in 1930 after having a long illness with tuberculosis, which disease had not yet yielded to effective medical treatment. His vow, should he recover, was to become a Christian, study the Bible and spread those ideas via art work.