The young Nationals looked like they were poised to stay in control for the rest of the match after taking a 70-66 lead with 3:47 left in the game.
South Korea, however, climbed back thanks to naturalized big man Ra Guna, who sparked a 9-0 run capped by a triple from Jeon Seonghyen to give their side a 75-70 lead with 2:26 remaining.
But Gilas stuck to its guns and slowly cut into the lead with four straight free throws before a steady Belangel found a wide-open lane to the hoop to put Gilas ahead 76-75 with 48 seconds remaining.
Kouame later had an opportunity to seal the deal for the Filipinos after drawing a foul on a big putback with 10 seconds remaining, but he missed the ensuing free throw, paving the way for a big transition 3 from Lee Hyunjung to tie the game with two seconds remaining.
This set the stage for the clutch dagger from Belangel, who came up with the biggest shot of his young career so far after a timeout from head coach Tab Baldwin.
Belangel finished with 13 points on 5-for-9 shooting to go with five rebounds and two assists for Gilas.
Ramos topped Gilas in scoring with 16 points, with nine of his points coming from the line, while Ange Kouame impressed in his debut as the program's newest naturalized center with 12 points and three triples, six rebounds, and one block.
Kai Sotto was solid in his men's debut as well, tallying 11 markers, seven boards, two assists, a steal and a block.
Yes sir!!!!! 🇵🇭🏀❤️🙏🏼 thank God!!!! #GILASPilipinas
— King Rivero (@ruzcko_rivero) June 16, 2021
SJ Belangel 💪🏼 pic.twitter.com/EmkzXneMjj