Fo is the guardian deity of the Black Order's Asia Branch, sealed by Bak's great-grandfather. Although she is not human, she often takes on a humanoid form to talk with others
Fo is not a human. She was created by Bak's great-grandfather. She was present during the time that Alma-Karma was at the Asian Branch and when he eventually went Berserk. She witnissed the ensuing deaths of the numerous people involved in the Second Exorcist program of which Alma Karma and Yuu Kanda were a part of.
Fo is a supportive protagonist created by Hoshino Katsura for the series D. Gray Man.
Not much has changed with Fo's character since her introduction.
Fo is of short stature and a lean physique. She has orange-ish colored hair that extends to her shoulders, but could be longer given that she always wears a rather unique purple/white hat. Her outfit matches her hat's purple color scheme and it consists of only bikini-like attire. She has green markings on her head and arms and her hands are finger-less and can be molded into different shapes such as her often scene scythe-like weapon.
Also, given that she is an artificial being, Fo does not appear to age. She is approximately 100 years old but has the appearance of a teenager.
Fo is a caring individual with a temperamental attitude.
Fo was the one who found Allen's nearly dead body after his defeat at the hands of Tyki Mikk. She took him to the Black Order Asian Branch Headquarters. When Allen came to, Fo took on the task of training Allen to regain his innocence powers he lost in his battle with Tyki. Her training was tough and was very much like a real battle, the only real difference being that Fo would not kill Allen. The training continued with ups and downs, but Allen made little apparent progress. Fo would cheer him up in the form of someone else so that Allen would not know it was her so that he would continue thinking of her as tough. But the two wound up developing a friendship anyway.
But when a level 3 Akuma attacked their headquarters in search of Allen, Fo was the only one present of good fighting caliber. She morphed into Allen's appearance so that the Akuma would target her instead. Allen was in distress, knowing Fo was not strong enough to face a level 3 Akuma alone. In his distress, he finally re-awakened his innocence, but this time the more powerful Crown Clown form as opposed to her former Cross form. As Fo was about to be defeated, Allen stepped in and destroyed the Akuma with relative ease, showing that his power was superior than before. Fo was in bad condition but did recover from her injuries.
Some time after the events of Fo and Allen training, Fo and Allen found themselves fighting together again. Fo was summoned by Bak through the stone that manifested her form. She took on a deranged Tokusa who was fighting Allen. She told Allen to take care of the more threatening Alma Karma while she took on Tokusa. But she noticed Allen's conflicting thoughts. Many things had changed since before and the fact that Allen was actually the 14th Noah was known. Allen was in the midst of contemplating joining the Noah in exchange for the Earl calling off further attacks to the exorcists. Fo tried to convince him not to do it, but while she was distracted, Tyki Mikk blindsided her and grievously wounded her on her back. But Fo was not finished just yet. From the ground, she implored Allen not to do it, but her stone was shattered and she immediately vanished. Fo is not a biological life-form so she does not die in the same sense, but she could be for all practical purposes be considered no more.
Fo can alter her appearance to look like another person, although she does not gain their abilities or properties. She can morph her hand into various things, usually bladed weapons like her large scythe-like appendage. Her ability does not seem to be at the level of Lulu Bell, who can change herself into anything of animate or inanimate nature.
Fo can communicate with others at will via telepathic communication.
Fo can create barriers and maintain them for extreme lengths of time. The entire Asian Branch Headquarters is surrounded by a barrier at all times and Akuma cannot enter through normal means. She maintained the barrier for in excess of 100 years. Whether or no Fo can create smaller personal barriers is unknown.