Actor Gong Yoo first mentioned about "Train to Busan 2" in his tweet. From then on, speculation about the cast arose including the enclosure of Song Jong-Ki.

After Gong tweeted in English about the sequel of "Train to Busan," calls for the second installment of the movie became viral. Many speculations arose about who will become the main cast for "Train to Busan 2."

The top hallyu star Song from "Descendants of the Sun" is mentioned as one potential candidate.

However, Song is recently busy filming the new film with veteran actor Hwang Jung-Min and So Ji-Sub, as TV Daily Korea reported. 

The movie is a story of about 400 Joseon people who want escape from Hashima Island after they were captured by Japanese imperial force during invasion to Joseon. They were taken to the island as forced laborers in a coal mine where they would work until they died.

Hashima was called Battleship Island because its shape resembles a battleship. Song is cast as an independence group member Park Moo Young, who infiltrates the island to rescue a leader of the group. Hwang portrays the role of bandmaster who was deceived to be one of the laborers to protect his daughter.

So's character, the best fighter in the ancient Seoul, is Choi Chil Sung. "Battleship Island" is directed by Ryoo Seung-Wan. This is his second to work with Hwang after the movie "Veteran."

Meanwhile "Train to Busan" has already gained huge success in international market. 

South China Morning Post reported that the movie has become the most watched Asian cinema of all time in Hong Kong. Within the first 34 days, it has grossed HK$66.3 million (US$ 8.5 million).

More than that, the movie has become the highest grossing zombie film in Hong Kong history, surpassing "World War Z. Therefore, it is reasonable that people expect the movie to have its sequel.