Update (June 29, 10:30pm EDT): Korea's Dispatch outlet reports that Rain and Kim Tae Hee flew back to Seoul this morning on the same flight -- Korea Air's KE5830 from Guangzhou -- but boarded separately.
According to an onlooker at Seoul's Incheon Airport, "As soon as they got off the flight, they started walking separately."
"When they went through customs they used different gates Rain showed up first and Kim Tae-hee came out of a different gate 30 minutes later."
Photos of the pair show the two going to great lengths not to be seen together, wearing surgical face masks and casual clothing.
(June 29, 5am EDT): Since they started dating almost three years ago, Rain and Kim Tae Hee have never officially stepped out in public together as a couple. But on June 28, the couple took a step closer to a public debut when they both attended an event in China.
Both Rain, 33, and Kim, 35, were guests at a 10-year anniversary event for Chinese cosmetics brand JVJQ, a company for which they are both been spokesmodels for.
And despite arriving separately to the Hainan bash, sources say the pair remained close once they were inside, although their stage time was separate (due to promoting different products).
It marks the first time the star couple have attended the same public event since the declaration of their relationship in January 2013.
Stay in the know about Rain and Kim Tae Hee by following IdolWow! on Twitter
Bizzarely, Rain’s rep says that the event was host to "many stars besides the two" idol stars and Kim's spokesperson stresses that the pair did not explicitly attended together, pointing out that fellow actress Kim Hee Sun was also in the list of guests: "They attended as models. They didn’t go together."
While it's no secret that the two are together (they have confirmed the relationship themselves), they seem to be at pains to keep their relationship away from the public eye.
Kim Tae Hee is currently preparing for her first TV comeback in two years for upcoming SBS drama Yong Pal, which will air in August.