After Manika accounted for host nation's Caroline Kumahara 11-5, 9-11, 12-10, 11-5, 11-5 to take the Under-21 women's singles crown, Ghosh defeated Benjamin Brossier of France 8-11, 6-11, 11-7, 11-6, 9-11, 11-7, 11-2 to win the men's singles title.
The Indians also pocketed USD 1500 each for their title wins.
"I have played Caroline before this year and won the team event in the Slovak Republic," said Manika.
Manika varied her speed and used a lot of backspin to dictate terms throughout the final.
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Ghosh, who had beaten teammate G Sathiyan in the semi-finals 11-4, 11-7, 14-12, 9-11, 11-9, knew Brossier would be a hard nut to crack.
Though Ghosh was up to the task, the Brazilian was time and again breathing down his neck in the final which saw fortunes fluctuating.
The Indian, however, had the measure of his rival, particularly in the decider, taking a 4-0 lead. Pumping his fist and more vocal with every point, Ghosh stayed closer to the table to finish the job in style.
Meanwhile, Sagarika Ghosh won the Cadet Girls singles title while Birdie Boro had to be satisfied with a silver in the Cadet Boys singles at the Guatemala Junior and Cadet Open Table Tennis championships.
Sagarika, the winner of South Asian Junior title recently, beat Sreeja 11-6, 11-5, 11-8 to take gold in the final.
Birdie Boro lost 9-11, 8-11, 5-11 to Cuban Livan Martinez in the final of the boys singles event. Earlier, Boro had beaten teammate Anirban Ghosh 3-0 to enter the final.