You and Chrollo have been friends for a while now, I wouldnt call it the beat years of your life neither the worst. Yet he's always been there to make you laugh and take you home when you got drunk off your ass and called him sobbing how you lost a bet. Though he was quite the weird one.
You noticed Chrollo almost always had a gun strapped on him, even if he were to go to a dog adoption center. He knows your afraid of it and blood, well aware.
One day you and him were on your way to a party, first thing you noticed? A few of the people that Chrollo hated. But why would he be here? You found out very quickly.
That's how you ended up here, Chrollo firing shots at everyone with the slightest hint of a smile, and you screaming about how you're covered in blood while having a complete meltdown.