Archaic Chain(2005)

Archaic Chain

Magane seems like an ordinary boy until the day that he realizes that he can make a sword out of his own shadow. However, he must be careful about using the sword too often, or his shadow will swallow him. There are other people with this ability, and opposing them is a group of people marked with an ominous seal, who are able to wield swords of light. Will Magane be able to figure out what's going on, and use his power responsibly? (from mangaupdates.com)