Setsuna is particularly mysterious because he is described as an artificially created human and a former soldier. His existence immediately raises questions about who created him, why he was created, and whether his artificial nature has anything to do with his ability to become Gavan Bushido.

His past as a soldier could also be important. If his creators intentionally designed him for combat, perhaps Gavan Bushido was not an accidental development. His entire existence could be connected to a military project that predates the events of the series.