That teenager, called "Kim," disappeared in a southern Turkish border city earlier this month, leading authorities to suspect that he may have slipped away to Syria to join ISIS.
While police have not concluded that he joined the terror group, authorities found he had a keen interest in the Islamic militants. Using a Twitter profile picture of an ISIS flag, he frequently tweeted, "I want join" and asked to meet "brothers." He followed pro-ISIS accounts and often retweeted the group's propaganda.
On his social media posts, he claimed he was from Chechnya, and lamented that "male are being discriminated against."
"I hate feminist," he said, according to a post on his Twitter account on October 5. "So I like the isis." He retweeted Arabic posts and tweeted in English, but never in Korean.
His last tweet was sent on October 10 -- which was the same month he began asking his mother if he could go to Turkey, according to Seoul Metro Police Agency.
Kim's mother told police that she had not been aware of his interest in ISIS. CNN was unable to reach Kim's parents.
South Korea may not be a probable place for aspiring ISIS members -- with less than 0.3% of the population identifying as Muslim. But ISIS has expanded its reach globally.
The Islamic militant group has attracted disaffected youth from around the world -- including the United States, France, Europe and Australia. There have also been reports about recruits joining ISIS from Asia, triggering concerns in the region.
Earlier last year, there was a report of a Chinese fighter caught in Iraq in September.
It's unclear how many Chinese nationals may be fighting with ISIS, but one former Chinese special envoy to the Middle East said there could be about 100. It remains unclear if some of them are Uighur, a Muslim minority group in Xinjiang.
Approximately 350 Southeast Asians were estimated to be in Iraq and Syria, said a Singapore official during a Security Council meeting in November.
Currently, two Japanese hostages are held by ISIS with a demand for $200 million ransom.
The mystery of Kim
South Korean police found about 517 searches for words affiliated with ISIS, as well as over 50 images of ISIS members toting guns and holding women in Kim's computer, they said.
In another social media account, Kim posted: "I want leaving my country and families just want to get a new life."
Reza Aslan, a religious scholar and adjunct senior fellow at the Council on Foreign Relations described a profile of young people who seek to join ISIS as feeling "dispossessed or marginalized. They feel somewhat they're having a crisis of identity."
"The assumption is that the religiously zealous are the ones joining ISIS, but that's not proven out by the data we have so far."
Kim began liaising with an individual whom he met on Twitter over an encrypted messaging service, police said.
On January 8, he arrived in Turkey with a Korean guardian. Two days later, he disappeared from a hotel in Kilis, a city near the Syrian border. His guardian reported him missing to the South Korean embassy in Turkey on January 12.