Here is a link to a website created by his grandchildren and which provides many more images of his work and information about his prolific and notable career. I think this image, with the playful color and simplified geometry used to describe the landscape, shows how Hiratsuka masterfully merged traditional Japanese and modern Western art influences.
The top of a pink mountain peeks over the edge to spy on the river. Swaths of autumn trees and evergreens partially obscure the mountaintop's view. But it can be seen that the river is calm and clear. The surface jiggles and sways a bit as it works around rocks and bends in its natural flow toward the someday sea.