Mana Intoxication
It's the acute poison of normally harmless mana that exists not just within the body but everywhere and within everything that exists around a person. Mana was everywhere; it was even within the air itself. As it was possible to suffer from both air and water intoxication, it was known to be able to suffer from mana intoxication as well. This was only possible for mana and mage users; however, as no user of ki was able to achieve this unique type of intoxication, they couldn't do so. Ki users were unable to suffer this because they could never obtain the level of mana required to pull it off. There were no ki users in existence who had ever suffered from this affliction because the human body is not born with that amount of mana in the first place, as a person's internal mana is set from birth. No person is born with that much, even as a birth defect, as too much internal mana is indeed considered a birth defect, as it's too much of a good thing after all. How is someone who was literally just born supposed to deal with an internal mana that dwarfs some adults from the moment they are born?
That person, however, would struggle constantly through their life without being in the ideal scenario and the ideal family to somehow manage the effects of having too much internal mana within themselves, though. It was a fate that was considered one of the worst way to go out and also something that happens within certain families as well that have members where that unborn child develops this defect and thus actually die in the womb from it, and/or the mother has to have the pregnancy ended because it could affect or even threaten her life as well. Acute mana intoxication was dangerous to those who could not properly manage their own internal mana at an insanely high level. If undetected within time, it was the silent killer of pregnant mothers after all.
The unique mage that had decided to follow leads on those that had suffered from this affliction through accident or on purpose led them to two interesting cases that caused them to think that they were getting close to seeing at least a glimpse of the truth from the Path of the Mana Blade itself. The fairy tale might be true to a lower extent than what people expect, but what if the person the true version of events was based on was a once and not just a million, not just a billion, not even a trillion, but vast beyond the beyond. This was an individual who took the idea of breaking the limits to the logical extreme, and thus it was highly unlikely that anyone like them would be born again. If they were, then one would have to hope that they were of the same moral character and personality as well.
The two mana users would, of course, be mages since they could not be anything else after all. Ki users were not capable of producing anyone who reached this level regardless of the scenario. It was just not possible, at least for humans, given how they are built and designed after all. Though the first case they had come across was someone who was born into a family of master blacksmiths that forged countless weapons for countless ages and generations. Somehow this family of blacksmith were also ki users that used mana in the creation of their weapons and whatever else they created within their smithery. The mother was someone who was not exactly the family heir or even from the main family itself, but she was obsessed with creating and forging anything and everything that came to her mind. She did this regardless of the time or even her condition. Somehow, that allowed her to survive full term with a baby suffering from mana intoxication. It was unknown exactly how she did it, but she managed to give birth to her child, who grew up around and helped their mother in her smithery from birth nearly. How someone like her managed to handle a child properly is considered a mystery to everyone, but the child was playing with blunt childproof weapons from birth. How their mother had such things was beyond anyone's guess, but they did because the child was alive and well to prove that, well, highly unlikely it was possible for it to happen.
This kid thus became unaware of what toys actually were until they were around others their own age. Proudly showing off their 'toys' and confused when the other kids did not know what to make of them. Even scaring the parents of the kids for thinking that they were harmful weapons, only to realize this was that woman's kid after all, and then just having them so that their kids would not play with them anymore. Did not really affect them that much because of their family being famous blacksmiths. Even if their mother was not a family heir nor within the main family itself. Just being a member meant she had people who got to know her and thus ended up actually befriending her somehow. Thus, their kids were allowed around her own so that her child did not grow up completely alone after all.
This kid's case of mana intoxication was from the effect of inheriting their mother's obsession with weapons, though, rather than making them their was with using them as they played with all the versions of the toys that their mother made for them. Over and over again until they wore out, and then they just got another and another one. The process would repeat itself for years upon years until the kid was pre teen, they woke up with heavily tanned skin, white hair, and steel color eyes. They themselves had become their own wand as they were a mage who was a weapon users. They had internal mana that was so high it dwarfed most adults at the grand master level. Yet the only thing they could do with their magic was create weapons that replicated whatever they played with growing up and/or learned about. They were a mage with no ability to use external mana, just depending on their own internal mana instead.