Shadow gunner

The greatest assassin and agent betrayed and reincarnated in the world of martial arts and martial spirits. Nathan was the most ruthless assassin with 0 failures in his mission report. Master in weponery, poison arts, hiding etc. After being in the field for 6 years he decided to leave the bloodshed and finally settle down. His dreams were crushed when he was backstabbed by his own country. When he opened his eyes he was in another world...a world of martial arts....a world with martial spirits... How will the former no 1 assassin will fare on this world.