The Demons Assassin (Black Butler/Kuroshitsuji Fanfic)

Two siblings. Born into a family that gave up on them. Raising and taking care of each other all their lives. They're always beside each other and sticking to each others side.
This is all they've ever known.... Well, aside from killing, of course. They had to make a living somehow.
So, they trained themselves in various martial arts and stealth and learned the ways of an assassin from the Romans.
However, they are completely caught off guard when Ciel Phantomhive offers them a job as his personal bodyguard.
Then, none other than Alois Trancy offers them a job when they turn down that one.
What can these two wonder twins do? What will they decide?
Read to find out!