Humans starting there mana core to awaken when they become 12 but even thought having mana core doesn't mean you well have a large mana pool. You still have to meditate and train for years to have an average mana pool.
"But what if i forcefully awaken my mana core before becoming 12 years old?".
There are unique cases where you can manifest your mana core forcefully while meditating for 1 day without someone disturbing.
But that was almost 200 years ago when the Great War era. Only some child who forcefully and have strong body that when the great war era can do. If a normal 11 years old will meditate they well only last atleast 1 hour even for noble or royal family prodigies can only last 5 hours. Because of need a high concentration that only adults can do.
There are no one in this era who want or who will force they're child to meditate without even awakening there mana core first. Because of the side effect of it that can destroy the mana core and can't use magic or aura again.
"But it's different for me, i already gone through meditating".
There are two main internal organ that can store the mana accumulated in meditating of magic or aura.
Heart and Brain
Brain manifest magic while heart manifest aura.
Magic utilize the mana surrounding the atmosphere and with an intention to manipulate and manifest.
While
Aura is the ability to have energy envelop the user. The user can release and surround themselves with energy. For defensive and offensive purposes, possibly granting them various abilities and attacks depending of the energy of the user.
You can only awaken one mana core, but there are cases when there's someone awaken there two mana core. They are called
[ Magic Swordman ] that can use both magic and aura.
There are only one magic swordman in the human race.
"Thinking of it pissed me of"
Because the magic swordman he mentioned is none other than the strongest human race in the world [ Arthur Windward ].
"Just wait Arthur, i will take my revenge when i settled the dragon attack first".
Leo who knew how to obtain the magic swordman, because he once heard it on Arthur when his drunk.
*
"Why are you telling me this? It's an very important you know"
"Why thought?, it's not like you can become an magic swordman because you know the method and beside it not something you can do forcefully on a unawakened mana user. It's just that it's a method you can achieve by your self". Arthur with a serious gaze at Leo while saying.
"Ahh.... Yeesss, i understand".
"And beside only an Windward family know how to do it, because it pass down to us by our ancestors".
*
"Idiot, thankyouu for telling me the method don't worry i will pay the price by killing you". Leo with a smile on his face.
Leo confront his family in said that no one is allowed to enter his room and explain the reason, of course they are shock because Leo wanted to train, because Leo one's known as an good for nothing, but they agreed and not let anyone enter the room.
Of course being able to awaken both two mana core is very difficult because it need a high concentration and if it fail, it can cause of mana spread to the body that can lead to death.
"if i only awaken one mana core that wouldn't be enough, even thought it well be more easy, i still need to be more powerful".
"Because i need to prevent so many disaster that coming".
You can only awaken one or both mana core together. Cause if you are awakened and try to open the second mana core, that can cause death. For example:
If you are awakened aura user all of the parts of the body like veins and bone will focus on your heart and if you forcefully awakened your second mana core, that will cause of confusion and malfunction that can cause of a coma or death.
That's why it need to awakened both mana core together if you want to obtain both without effecting your body. But it's a very hard method that Arthur said to him.
"It will be more easy if i have the scroll that Arthur said, i only remembered what he said".
"Will i really be able to do it? No i have to, besides i'm once an 8 star mana user".
Leo started meditating.
*
"What you need first is concentrate and connect thousand of fragments of mana".
"Next is cut it to half and put it in the heart and brain, of course it would be easy if you have the scroll that our ancestor have".
"Because if i don't have that i'm actually died right now".
"Do you know what scroll it is? Guess it!, guess it!". Is what Arthur said.
....
"It's a scroll that make the flow of time slow at an small surrounding area that last 14 days, and the real flow time is actually only 1 day pass".
"That's why it's impossible if you don't have the scroll".
"Even thought the method is easy to say, without the scroll, it's an extreme difficult method, it atleast make me 1 days to fully complete it with the scroll, if it's not because of the scroll it would atleast take 14 days to fully do it and that there's no record of human that actually it".
"That's why the high beings come up with the method "time flow method".
"Ahhh, so that's the reason". Leo replied to the story of Arthur.
"Right? HWHAHAH".
"because you still don't have a mana core, to actually absorb the mana itself that's why it hard".
"Because if you have the mana core, while meditating, the mana core is the one that absorb the mana, that's why it's very hard if you still don't have a mana core because you are the one that need to gather it infornt of the mana core to forcefully awaken the one mana core".
"And it even harder if you wan't to have both magic and aura because you have to cut the fragments of mana to half and put it to your brain and heart, while still need to wait 5 day to break the mana core because it's only a half fragments of mana that gather".
"Why are telling me this? It's an very important you know?". Leo asked.
"Why thought?, it's not like you can become an magic swordman because you know the method and beside it not something you can do forcefully on a unawakened mana user. It's just that it's a method you can achieve by your self". Arthur with a serious gaze at Leo while saying.
"Ahh.... Yeesss, i understand".
"And beside only an Windward family know how to do it, because it pass down to us by our ancestors".
*
Leo start meditating and gathering the mana that scattered to his body.
3 days passed
Leo completly gather all of the fragment of mana and he start cutting it to half, later he know that was the start of the life threatening method because of the exhausted body of his.