This was the second consecutive victory registered by India in the tournament.
India beat China 3-0 in the tournament opener.
Sukhjeet Singh (2', 60') scored a double in India's win while Abhishek (3'), Sanjay (17') and Uttam Singh (54') scored a goal each to destroy the Japanese attack.
Japan's Kazumasa Matsumoto (41') scored the single goal for the side.
Sukhjeet Singh commenced the match with a bang by scoring the inaugural goal in just 2 minutes into the game.
India soon extended the goal margin to 2-0 after Abhishek dribbled past multiple Japanese defenders to drive it around the goalkeeper to score.
India continued the dominance the extended the goal margin to 3-0 when Sanjay converted a splendid penalty corner in the 17th minute.
Kazumasa Matsumoto reduced the goal difference to 3-1 in the 41st minute.
However, Jarmanpreet Singh, who assisted Uttam Singh from the baseline to convert a fine field goal in the 41st minute, helping India to take 4-1 lead in the match.
Sukhjeet added another goal to his name in the 60th minute to complete India's 5-1 win in the second match.
India have remained unbeaten so far in the tournament.
India came to the tournament after winning bronze medal in the recently held Paris Olympics.