The Humani Chronicles
When his sister Kyana is forced into the light layer, Rekon’s determination to find her causes him to cross halfway to her before being rejected, since he did not go through the Gatekeeper to do so. As a result, he is permanently able to cross halfway, allowing him to turn into a shadow, but lost all of his memories up to that point to prevent him from trying again. He can bring those he touches into the shadows with him. He becomes good friends with Daniel and helps fake his death and convince him to live life to its fullest.