One Night Stand Couple

The Cold hearted yesung who only do one night stands and The Playboy kyuhyun who is never serious about anything besides his work, both of them spend one night stand with each other
Kyuhyun becomes interested in yesung after finding out about his past and After meeting several times with each other by coincidence, kyuhyun suggest that they'll become sex partners

After refusing kyuhyun offer multiple times not wanting to lose his life style, yesung finally acceptes his offer, What will happen when yesung accept kyuhyun suggestion?