who are they

According to Google translated comments on this page they're cheerleaders. Probably baseball or basketball since that's pretty huge in South Korea.

https://www.vingle.net/posts/1914574

Edit:

Yes, they're cheerleaders for the 부천 KEB하나은행 여자 농구단 (Keb Hana female basketball team). They're not players as the players wear longer shorts.

Here's another photo of the crew:

http://www.xportsnews.com/?ac=article_view&entry_id=679743

According to Google translated comments on this page they're cheerleaders. Probably baseball or basketball since that's pretty huge in South Korea.

https://www.vingle.net/posts/1914574

Edit:

Yes, they're cheerleaders for the 부천 KEB하나은행 여자 농구단 (Keb Hana female basketball team). They're not players as the players wear longer shorts.

Here's another photo of the crew:

http://www.xportsnews.com/?ac=article_view&entry_id=679743