Jeje struck from the penalty in the second minute and completed his brace in the 82nd minute while Sony Norde, making a return, also made his presence felt as he netted the ball in the 87th minute. Hussain Nihan scored an own goal in the 45th minute.
Godfrey West Omodu, who had struck a solitary goal in the first leg, reduced the margin with his 52nd minute strike.
Mohun Bagan started the return leg with a bang when Ahmed Usam's handball inside the box earned them a penalty straightaway in the first minute with Jeje easily slotting it home for an early lead.
Jeje and Sony kept on attacking but they had to wait till the stroke of break for a 2-0 lead with Nihan's own goal.
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Balwant set up the fourth goal for Katsumi to slide it sideways and Sony smashed it across the face of the goal to complete the rout.
Jeje scored his second with Katsumi Yusua surging down the centre and finding Prabir Das down the right as he brilliantly curled in for the Mizo striker to finish.
In the first leg, Club Valencia striker Godfrey West Omodu nullified Darryl Duffy's sixth minute lead with his strike in the 71st minute and Mohun Bagan had to settle for a 1-1 draw.