Here's at least one reason to watch the drama 'The Merchant: Gaekju 2015' - you can hear f(x) Luna's OST in it! Luna lent her beautiful vocals to the drama for the track "Only You".

It's a dramatic ballad song described to have a soft piano background and a beautiful melody. You'll notice how soothing and lovely the OST is.

Be sure to take a listen to "Only You" above and watch 'The Merchant: Gaekju 2015'!