HUDDLED over the viewfinder of The Straits Times photographer's camera, North Korean sisters Kim Hye Song and Kim Hye Gyong giggled excitedly as they pointed at images of themselves.
This brief moment of girlish spontaneity belied their default sombre facade, and allowed a fleeting glimpse into their identities as national athletes from a country shrouded in much secrecy.
Soon, the 20-year-old twins - touted as the future of women's marathon running in North Korea - were whisked away with all interview requests rejected, ahead of the Great Eastern Women's Run.
Their entry onto the world stage, however, was not that muted.
Coming from relative obscurity, the younger Hye Gyong stormed to an eighth-place finish in the marathon at August's World Championships - in only her second overseas competition.
Running under hot and humid conditions in Moscow with temperatures rising to 34 deg C, she clocked 2hr 35min 49sec to mark North Korea's only top-10 finish in the women's marathon at the championships since 1999.
Hye Song also competed that day, finishing 14th in 2:38.28.
Jong Myong Chol, their coach of seven years, believes that the sisters enjoy a healthy rivalry which has spurred their development over the years.
Speaking through a translator, he said: "Although they are sisters, they are also competitors to each other so they challenge each other and they push each other during their races.
"I train them to challenge each other but only during the race.
"Once it ends, they are friends and sisters. There might be a difference in their (race) positions but there are no problems at all."
Outside the sporting arena, Jong said, the sisters have distinct personalities. Hye Song is more conservative and quiet compared to Hye Gyong.
The younger sister, adds Jong, tends to put in a bit more effort in their 25-30km daily training sessions, which take place five times a week.
Tomorrow, the North Korean pair - who were invited by the organisers to participate - are among the favourites for the 21.1km race at The Float@Marina Bay.
But they will face tough competition from Japanese Yuko Watanabe, 26, who won last month's Sapporo Marathon in 2:29.13.
Said the North Korean coach: "I can't say whether they can win but I have high confidence in their personal results.
"The weather condition here is good so far and I trust my runners."
Local hope Lim Bao Ying, however, is hoping that the Singapore heat will prove a stumbling block to the foreign competitors.
Said the 31-year-old who has a 21.2km personal best of 1:31: "I'm really impressed by the Japanese and the North Koreans' timings.
"But most of them are used to cooler climates and, hopefully, the weather here might slow them down."
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