"I'm so fond of the charming young hero. I have changed all the wallpaper on my phone and laptop to his picture," says the postgraduate student in Beijing. Wang has set up a fan group with 20 other girls in her class to gossip about the series through the mobile app WeChat.

Wang is just one of a growing army of fans who have fallen in love with new TV imports they watch online. Domestic online video firms are scrambling to secure rights to broadcast foreign TV shows.

It is not only South Korean TV. Western series are also immensely popular in China. The new season of the US political drama House of Cards is drawing legions of online viewers with its China-focused plot lines that touch on the escalating tension between China and Japan in the East China Sea.

The second season of the political drama premiered on Feb 14 on Netflix in the United States and on Sohu.com in China. It is the most-watched US television show on Sohu, with more than 19 million views as of Feb 22.

Watching TV imports online has become indispensable entertainment for a large number of young people in China. Originally, the desire to learn foreign languages prompted a few people to watch imported TV, but things are very different today.

"It's not just for fun. Watching American TV shows is a great way to understand culture and politics, too," says Su Zhou, 26, an editor based in Beijing.

As TV imports gain popularity among young people, the way of viewing them has evolved from traditional TV networks to the desktop PC to mobile devices. The arrival of 4G mobile should mean even more foreign videos on even more mobile devices.

"I used to buy pirated DVDs but now I'm excited to watch House of Cards at the same time as it is broadcast in the United States," says Beijinger Zhang Xinqing.

"The Internet has dramatically changed the transmission mode of television programs," says Kuang Wenbo, a journalism professor at Renmin University of China. "More and more people use online video sites because they can watch a host of TV shows whenever they want."

In recent years, online video has grown bigger and more competitive in China. There were around 428 million people watching videos online by the end of 2013, up 15.2 percent, according to the China Internet Network Information Center.

Despite the size of the Chinese online video industry, domestic firms find it hard to make much money due to the high costs of broadcast rights and of delivering the content.

Chinese viewers can devour the video without charge, as long as they are prepared to sit through the advertisements that pop up before each episode begins.

Paying for premium content is a habit Chinese viewers don't have yet, says Ma Ke, executive director of copyright purchasing at Sohu. "Both Sohu and our domestic competitors try to recover our costs by putting ads in the content," says Ma, adding that only a small portion of their output is pay-to-view.