Fo is the guardian deity of the Black Order's Asian Branch, sealed by Bak's great-grandfather. The branch is protected by a barrier created by Fo, the "entrance". Although she is not a human, she often takes on a humanoid form. She shares a strong bond with Bak, but loves to tease him. She can manipulate her form to change her hands into axe-like weapons or to copy someone's appearance. She is also capable of communicating telepathically with others. Although she shows a "tough-love" attitude to others, she is a very caring individual. She helped train Allen to try to get his Innocence to activate.