"How can you not be freaked out?"
Jack is very inquisitive when it comes to the making of swords, and emotionally expresses himself by the sword that he carries, when he is having a bad day he will carry a black sword. He doesn't really have any distinct characteristics in his personality other then he is very protective over his little brother.
(Told by Jack) Hmm well that is a tricky subject. I am Jack O'Lanturen or Jack-O-Lantern I am of the highest calibur of demon hunters. I am most famously known for my work in the underworld. But after a single failed transportation circle I was subjected to become a demon.
Luckily for me the greatest demon lord's son thought of me as a pet. If it wasn't for this boy I would be a walking dead right now. That boys name was Ciel. I served the family well and became the lapdog of Ciel's father hunting down rouge demons and bringing them back to him so he could devour their souls and sustain his immortal life.
After gaining enough favor with the family I started to be accepted as one of them, or so I thought. Ciel and I became bestfriends and almost brothers, but it seems that his father favored me so he gave me the most sacred powers that were in line for Ciel, but this was only to seek out the next ruler of the underworld.
Ciel always despised that I received the most powerful rights a human could have and tried to devour me to gain the powers. Inside of his eternal stomach realm I awoken my first power, the power of Demon Blade forgery, it let me make a blade made of the most potent unearthly elements.
I tore Ciel's stomach open and tried to flee back home, but Ciel stepped on the circle which caused it to fail. I was combined with more of the demon essence which unlocked two more powers, the power of homicidal madness and the power of first step transformation. These powers were used together and I became a whole different Jack. I almost killed Ciel and if it wasn't for his father stepping in and stopping me I would have succeeded. The demon lords trained me well and I became more known as Jack The Pumpkin King.
But I digress, oh um what was the question again? Oh yes right, I am half demon and half demon hunter. A useful adaptation isn't it? Ciel has grown extremely hungry since I sliced his stomach open and he comes the the mortal realm to cause a bit of trouble and eat. I don't blame him for hating me, I did steal the family powers I guess.