India got the first scoring chance of the match in the form of a penalty corner but Japan goalkeeper Takashi Yoshikawa made a confident save to deny home team skipper Harmanpreet Singh.
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The Indians set pace of the game and enjoyed bulk of the possession, while Japan played catch-up hockey.
After a barren first quarter, India finally took the lead in the 19th minute through Akashdeep Singh, who slapped the ball in from a rebound from after Hardik Singh's initial shot was saved by Japan second goalkeeper Takumi Kitagawa.
India kept up the tempo and earned their second penalty corner in the 23rd minute and India skipper Harmanpreet sounded the board with a fierce low flick to the left of Japanese goalie to double India's lead.
Just at the stroke of half-time, India trippled their lead through Mandeep Singh.
It was Manpreet Singh who was instrumental in getting the third goal as he intercepted the ball in the mid-field and then beat three Japanese defenders to set it up for Mandeep, who just had to direct the ball in.
The trend continued after the change of ends as India continued to press hard on the Japanese goal.
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Sumit probably scored the goal of the tournament with a back stick flick into the net from a tight angle after being brilliantly set up by Manpreet hardwork from the right flank.
Young Karthi Selvam made it 5-0 in India's favour in the 51st minute after being fed by an unselfish Sukhjeet Singh, who received a perfect ariel ball from Harmanpreet.
India will take on Malaysia in the final on Saturday, while Japan will be up against defending champions South Korea in the third-fourth place play-off match.
SEMIS: India vs Japan hockey - As it happenedFULL TIME: IND 5-0 JPN
51st minute: Indian now making mockery of Japan. Karthi Selvam scored the 5th goal for India.
THIRD QUARTER: IND 4-0 JPN
39th minute: Yet another superb work from Manpreet in the mid-field. He feed the ball to Sumit, who foxed defenders to score India's 4th goal.
HALF TIME: IND 3-0 JPN
30th minute: Manpreet Singh displayed excellent skills against the run of play, beating three defenders he fires on in from the right flank. Mandeep Singh deflected it perfectly into the Japanese post to give India 3-goal lead.
23rd minute: GOALLLL! Harmanpreet Singh fires one through the Japanese goalkeeper as he successfully converts a penalty corner.
19th minute: India displayed a brilliant display of patience before unleashing the attack from the right flank. Though Akashdeep got the name in scoresheet, it was superb skill of Hardik Singh which made the goal possible.
First quarter: IND 0-0 JPN
First quarter went goalless. India did get a penalty corner but Japanese goalkeeper was rock solid in front of his post.
2nd minute: Jarmanpreet earns a penalt corner but Harmanpreet Singh failed to convert.