Here is a very fine story coming from springrain authornim for Black Suits series

The story http://www.asianfanfics.com/story/view/609390/a-foundation-of-lies-black-suits-1-angst-gangs-romance-you-exo-kai-kyungsoo

Sequel http://www.asianfanfics.com/story/view/763711/forged-black-suits-2-angst-gangs-romance-you-exo-kyungsoo