From http://en.wikipedia.org/wiki/Shizo_Kanakuri

Shizo Kanakuri (Japanese: Kanaguri Shis? or Kanakuri Shiz?, August 20, 1891 – November 13, 1984) was a Japanese marathon runner and one of the early leaders of track and field athletics in Japan.

He is best known for disappearing during the marathon race in the 1912 Summer Olympics. He abandoned the race due to the heat, and returned to Japan without notifying race officials. Swedish authorities considered him missing for 50 years before discovering that he was living in Japan and had competed in intervening Olympic marathons. In 1966 he was contacted by Swedish Television and offered to complete his run. He accepted and completed the Marathon in 54 years, 8 months, 6 days, 8 hours, 32 minutes and 20.3 seconds.

He also competed in the 1920 Summer Olympics, where he finished the marathon race in 2'48:45.4 hours and placed 16th.

At the 1924 Summer Olympics he again failed to finish the marathon.