Indonesia's Anthony Susanto was made to work for his win though Japan's Miyo Kobayashi had an easier time at the court during yesterday's 48th Brunei International Tennis Federation (ITF) Junior Circuit action.
The top seed in the boy's singles, Susanto lost his first set 4-6 to unseeded Kanji Tokunaga but came back strongly to take the next two sets 6-0, 6-3 to move to the third round.
His counterpart in the girl's singles, Kobayashi defeated unseeded Indonesian Valencia Alberta Sudibyo 6-4, 6-2 to proceed into the quarter-finals in the girls' singles.
Susanto felt that the weather got in the way of his game at the National Tennis Centre of the Hassanal Bolkiah National Sports Complex in Berakas.
"I don't think my body has got accustomed to the weather here yet and I felt really tired," said Susanto, who received a bye into the second round.
"I was also really confused because all of the grounds here are different to each other. One side has fast courts and the other is slow.
"During the first set against Tokunaga, instead of playing 100 per cent I had to resort to only playing at 30 per cent of my capabilities because my chest felt really tight.
"I finally found my flow and I easily defeated Tokunaga 6-0 in the second set and 6-3 in the third.
"I do hope to win the tournament," added the Indonesian.
Susanto was also present during the 47th edition in March but crashed out in the quarter-finals after going down to compatriot Nuradim Ramdani 6-2, 6-3.
Watching Susanto was his coach Elbert Sie, who felt his athlete played really bad.
"He underperformed today and it was bad," said Sie in an interview with The Brunei Times.
"Maybe it was because it was his first round playing and he is still trying to get used to the rhythm of the court and weather.
"I hope that he can play better in the next few rounds.
"My aim for him is to be the champion of this competition because he is the first seed.
"When I watch him I can see that he is capable of winning this tournament if he is playing his normal game," added Sie.
Susanto and Christian Alvin Edison, also under the wings of Sie for the circuit, moved to the quarter-finals of the boy's doubles after taking down American Jack Pulliam and Philippines Joachim Samson 6-2, 6-2.
Singapore's Joshua Liu and Thailand's Vorachon Rakpuangchon, who are number one seeds for the boy's doubles, progressed into the quarter-finals after defeating Hong Kong's Cheuk Yin Yuen and Thailand's Pattanapong Borisutpong - who were unseeded.
In the girl's doubles, the number one seeds, Kobayashi and Indonesia's Arrum Damarsari had a bye which moved them into the quarter-finals - where they will challenge Indonesia's unseeded duo, Devi Hasan and Sudibyo today.
Local hopes died on Tuesday when Nurul Mohd Andi Hambali and Law Vi Chen were knocked out of the competition in the first round.
Nurul Mohd Andi was eliminated 7-5, 6-1 by Jerome Romualdez while Law suffered a 6-0, 6-0 loss to Samson.