Dan Heng is the reserved train guard and archivist of the Astral Express, a train that travels through space, visiting different planets. He wields a spear named Cloud-Piercer, he joined the Express crew to escape his secluded past back in his home planet. Dan Heng is a distant and a very socially reserved person, which is interested in reading books and taking care of the Data Bank in the Astral Express, which is also his room.