The Walking Major(1970)

In wartime he fought! In peactime he walked!

U.S. Army Captain Clark Allen gains attention by walking back and forth, the length of Japan, gambling with U.S. servicemen in order to raise funds to rebuild an orphanage. Suspicious of Allen's motives, a Japanese newsman, Hiroshi Kitabayashi, traces the American's background until he discovers the motive behind Allen's long walk.