As Jane found out, making a fire with magic was neither simple nor complicated. Combining the runes for 'Fuel' and 'Heat' made a small mass of flaming substance, and adding in 'Air' made it self-sufficient and more powerful. He would have directly covered his body in messy 'Heat' runes, but that sounded like a horrible way to die if he made a mistake. So, he constructed 'Fire' spells at regular intervals around him, and opened his body up to dry faster.
Even once he was mostly dry and warmed, the mana used in making the runes didn't dissipate. It didn't take any mana to keep a rune active, but it did take concentration, and the mana used for the rune wouldn't be restored until it was undone. If Jane wanted to, he could keep the fires going for hours straight. There was no reason to, though.
The day was already ending, yet Jane had barely done anything besides collecting vegetables. Silently cursing his teacher, he headed back with what little was left in his basket. His brother was going to start making dinner soon, so Jane needed to get the vegetables to him before that.
---
Although it was shameful as his kin, Jane did not know his brother's name. For as long as he knew, after all, his brother had been unable to speak. To make matters worse, although he himself was a little literate— he had picked up bits and pieces from context clues— his brother could not read or write a single word. Because they could barely communicate at all, the two brothers more or less kept to themselves. Perhaps it was exactly because they could not communicate, but their tacit agreements were entirely clear to them.
No matter what Jane did, his brother would surely forgive him for it. After all, with how difficult it was to survive, he knew he didn't have any time to waste on useless things. And so, there was no real scorn on his brother's face when Jane returned dirtied and without enough vegetables for their dinner. At least that much trust was necessary between the two.
In fact, with how uncertain the future was for him, Jane couldn't help but rely on that trust to keep moving forwards. There was no guarantee that his efforts to learn magic would bear tangible fruit, and no telling if he would randomly be whisked away to some horrible place. Those things he would say to which his brother could not object were the hardest, and so he had to be absolutely sure before saying them.
And if they were given the chance, the brothers would talk for the first time in their lives. No, Jane would create that chance by himself, no matter what it took. That was the least which he owed to his brother.
---
Jane chose not to learn new runes today, but instead to practice refining and condensing them. The incomprehensibly developed runes which his teacher threw out like candy were at the same time demotivating and a goal which he needed to reach. He knew it was possible to reach, too. He just had to put the work in.
'If that idiot can do it, why wouldn't I be able to?'
Soon, the symbol for 'Heat' was in the air. Jane stared at the blurry and misshapen structure, and thought of the rune as it appeared in the book. Moreso, he thought of the sharp lines of his teacher's magic. He focused on the mana forming the rune, especially the messy bits, and drew them closer to the skeleton of the rune. When some areas were thin, he distributed more mana to them, and when the shape of an area was ill-defined, he remade it. As he refined his rune, the heat in front of his face grew more and more unbearable. Just as he was making his final correction...
"Ah! Shit— Ow ow ow ow!"
His eyebrows caught on fire. The meticulously constructed rune fell apart immediately, and Jane began smacking his face repeatedly in an effort to put out the fire. He soon put a hasty 'Water' rune together, and soothed his burnt face in the cool liquid. Despite the pain pulsating in his brows, his mood had gotten a little better. Even if it was just a little, he thought he could see the path his teacher took to become so skilled.
Jane locked away the runes which would cause too much of a mess or harm him, and ended up refining only the 'Air' rune. A cool breeze began to fill his room, then a gale, and even unbearable winds which whipped his hair in every direction. Jane let the trembling mana disperse, and tried again.
This time, the rune was a little bit smaller than before. The effect was lesser, as well, proving his teacher's rant about quality to be true. However, this was something he could fix.
Jane once again began refining the rune to the same quality as the larger one. As he refined it further and further, the effect began to come close, but still stopped just short of the earlier effect. He had missed something, somewhere.
In the midst of the howling winds, Jane stared at the rune. He stared a bit longer, searching every last inch of the rune's structure.
'Hmm? It looks a little blurry there.'
The tiniest bit of mana was clouding one of the bends of the rune. Jane fixed it, and soon, the effect from before assaulted his body. He once again dispersed the mana.
'Now, time to do this again...'
He gathered his mana for the fourth time. In front of him, a similar rune stood, except this time it was even smaller. He resolved to repeat the process, at least until his runes looked like his teacher's.
---
Long before he reached that point, though, he ran out of mana. Still caring for his old method of training, he began taming ambient mana again. He once again focused on where his soul core should should have been and...?
'What's that?'
Right underneath his skin, the faintest bit of obstruction could be seen. Jane hurriedly focused in on that portion, trying to see what it was.
Cutting through the layer, thousands upon thousands of imperceptibly tiny symbols were etched. Even trying to read even a portion of them gave him a humongous headache.
'Genuinely, what the hell?'
Jane focused on another portion of his body, instead, and found traces of runes hiding just underneath the surface. In fact, everywhere he looked, his body was concealing incredibly dense runes carved through a surface to such a degree that the it was hardly visible. Jane had a slight suspicion.
'Is this why I couldn't find my Manaheart? It was this big?'
Despite how impossible it seemed, the layer underneath his skin could only be the outer shell of his Manaheart. The one which he couldn't find for all this time, it was in fact so large and so heavily modified that he could not even recognize it. If his perception had not increased, and his tamed mana had not increased the space on his outer shell, he would not have even noticed such a thing.
Even more concerning than the size of his soul core, however, was the runes on it. He recognized it to be the engravings his teacher spoke of, but he seriously doubted this was within the realm of what was humanly possible. In a fractal-like manner, every single inch of runes was, in fact, composed of even smaller and even more intricate rune structures, continuing on well past the point where Jane could sense them.
Through those runes, a torrent of mana was constantly being released, and then it lingered in the air before returning back to the soul core. Just as his teacher said, Jane had no control over the mana which was cycling through the runes. All he knew is that it was an inconceivable amount.
'If I reach my teacher's level, will I be able to decrypt those runes? Wait, even he might not be able to see through these... Do I just have to train for hundreds of years before being able to read them?'
Even though he felt not yet tamed mana escaping from his soul core, he could not bring himself to exert control on it. There was simply too much on his mind. Now, he had confirmed that there was actual magic being constantly cast by his soul core, but he still had no idea what it was. It was simply too powerful, too vast, for him to comprehend. At least, for now.
'I won't suddenly explode and wipe out the continent though, right?'
He chuckled a little at the outlandish thought. His expression quickly turned to a frown, though, realizing that he genuinely might become a world-ending bomb.
'At the very least, my teacher will die with me.'
Thinking this, he felt a little better.