Inoue crossed the finish line of the 42 km course in two hours 18 minutes and 22 seconds reports Efe news.
Bahrain s Elhassan Elabbassi bagged silver while China s Bujie Duo won bronze.
The rest of the top 10 places went to athletes from Japan Mongolia North Korea China Thailand and Uzbekistan.
Inoue s gold was Japan s 30th and the country sat in second place on the medals table on Saturday morning with a total of 104 behind leader China with 140 and the Republic of Korea in third with 78.
--IANS kk/ksk
