I actually drew that fanart last fall, but it was "lost" for a while until I found it while cleaning my computer up. So I finished it and here it is.
Chrono Crusade is basically about Sister Rosetta, a nun exoricist who happened to be partnered with a friendly demon named Chrono (not sure of spelling), and she tend to leave behind a trail of destruction while trying to exorcise a demon.

It's a very amusing story with a sad ending. Just in you're wondering, she's getting yelled at by her superior via telephone connected to Chrono's backpack filled with exorcising guns and stuff.