Fremy is the Saint of Powder. Her unique heredity allowed her to receive from the god a type of power that no one ever received before her, as "Powder" isn't among the 78 officially known types of Saints. As such, she's also the only Saint who isn't under the supervision of Mora. Her power allows her to freely create explosives during battles, and greatly increases the damage caused by her gun's bullets. In Rokka no Yuusha's world, guns aren't powerful enough to injure a kyouma, but in Fremy's case, she can easily kill most of the kyouma as well as most armored humans in one single shot. But because her gun need to be reloaded after every fired shot, she's weak in close combat as well as when she's surrounded.
While Fremy's name is completely unknown publicly, she's widely known under the ominous name of "Six flowers killer." She received that name after going around assassinating potential future heroes of the six flowers, in order to only leave weak fighters alive. That way, when the time for the heroes of the six flowers to be chosen would finally come, the God of Fate would have only weak heroes as candidates, ultimately resulting in the heroes defeat and the complete awakening of the Majin.
Fremy is the first and only half human/half kyouma in the world. This is the result of Tgurneu's experiences, as he asked one of his minion to evolve in order to be able to copulate with a human and give birth to an half kyouma. She never knew her human father as he was killed after that her Kyouma mother became pregnant. She was raised by her kyouma mother and strongly believed to be part of the kyouma army. She devoted herself to obey Tgurneu's orders in order to prove her worth as an half kyouma. Fremy managed to assassinate several really powerful and well known warriors and Saints, and the rumors about the "six flowers' killer" started to spread quickly. However, she finally faced a problem a few months before the Majin's awakening against Chamo. Chamo's tremendous power not only protected her from Fremy's bullets, but almost killed Fremy who barely managed to escape alive from Chamo's wrath afterward. Because she was unable to accomplish her most important mission, she was deemed useless by her mother and the other kyouma who then tried to kill her as well.
Feeling betrayed by her own world as well as everything she loved, she then gained the strong resolution of killing the Majin, and finally received one of the heroes of six flower's mark. Since she knew that she would be killed if she were to encounter Chamo or anyone else knowing her past as the Six flowers killer, she first tried to reach the kyouma territory without encountering the other heroes. She's convinced by Adlet to do otherwise and then renounce to her wish to kill the Majin alone.
While she started of distrusting Adlet, he quickly became the only one among the seven heroes that she trusts. She suspects everyone else and is quick to point her gun toward any hero with a suspicious behavior.