The semi-final victory was also India's second in the tournament against Japan, having beaten them at the group league stage.
For India Mandeep Singh, Manpreet Singh Jr, Vikramjit Singh and Varun Kumar scored one goal apiece while Harmanpreet Singh struck twice, whose individual goals tally in the tournament has gone upto 11. For Japan, Yamada Shota reduced the margin.
India will meet the winner between Pakistan and South Korea, who are pitted against each other in the second semi-final scheduled to be played tomorrow.
Manpreet Jr increased the tally within a minute to make it 2-0. India did not need to look back after this and continued with their goal fest as Harmanpreet scored his 10th goal of the tournament from a penalty corner giving India a comfortable 3-0 lead.
Also Read
Vikramjit's field goal in the 27th minute consolidated India's lead to 4-0 as the winners went into the break.
Japan started the second half with an attacking intent and was rewarded with a penalty corner which was converted by Yamada Shota giving Japan a much needed breather.
(REOPENS FGN 9)
The 10 goals against Japan were India's highest since they scored nine against Bangladesh in the Asia Cup three years ago.
"I was here with the Indian team when they scored nine against Bangladesh and eight against Oman three years ago," said Oltmans. "Japan are a much higher ranked team than those two rivals, so I am quite pleased."
Oltmans is happy at the manner in which his players went out looking for goals in the first outing.
Oltmans said India came here with the intent of showcasing their goal-scoring prowess.
"We need to see the players perform in the field. We've got a good start and look forward to a a fine show in the next two games against South Korea and Pakistan," the coach said.
"Every opponent is the same and we will play our usual attacking game. Right now, we are focused on the match against South Korea after which we will prepare for the game against Pakistan," added Oltmans.