It was really quite simple, in the end. His teacher had used a decently powerful protective magic on himself beforehand, and so he had a degree of protection against all physical attacks. Because of this, despite being thrown around like a ragdoll, he still appeared completely fine. His clothes were not, however. Jane stared at his teacher's scrawny body through the holes in his robe.
"Finally, you look like you belong in the forest."
"My dear disciple, there is nowhere I do not belong."
Despite his shredded clothes, Calex still looked satisfied, and even hummed quietly. Jane knew why, of course.
The duel had two possible outcomes. If his teacher won, then he would get to enjoy the taste of victory. If Jane won, then his teacher could be proud of how he raised his student. No matter what happened, there would only be upsides for the mage.
"Ah, to have such a talented young magician here, I can only imagine just what kind of existence his master must be."
"Can you stop gloating? You lost, anyways."
"This is how master-disciple relationships work, you see. The disciple's achievements are the master's, and the master's pedigree is shared with the disciple. Is there a more mutually beneficial bond in the world?"
"Do you have anything else to say besides that? Like, tips on how to fight better?"
All this time, his teacher gave no meaningful feedback, but was instead feeding his own ego. As his student, Jane almost felt a little embarrassed— perhaps because he would have done the same in his teacher's position.
"There isn't much to say, my disciple. It seems you have a talent for attacking unmoving targets... Oh, you should be more or less ready to learn that now."
"What? Don't speak so ominously like that."
His teacher paused for a moment, deep in thought.
"My disciple, how do you think defense magic works?"
Jane reviewed all of the runes he had learned. All of the syntax, and all the runes which had an effect. He thought about the defense his teacher showed.
'How can I combine them, to make something like that... no, it's impossible. That spell didn't create anything physical.'
"I wouldn't know, since it uses runes I haven't learned yet."
"Incorrect. You are already able to use defense magic. While you can't use the same magic as me yet, any spell which negates the offensive effect of another can be classified as defense magic."
"Hey, did you purposefully make me think of the magic you used as the only defense magic just so you could—"
"Wasn't it your own fault for assuming that?"
'Damnit.'
"Okay, but some kinds of magic can't really be used as defense magic. Like, if I tried negating 'Water' or 'Air', I would be putting myself in serious danger. Isn't that why you use that all-rounder defense magic?"
"Correct. Out of all the spells which are classified as defense, mine is one that has the purest effects, and few downsides for the user. However, I will not be teaching it to you. You must invent it yourself."
'Like everything else, huh.'
Calex manifested a rune in the air, just large enough for Jane to make out. A gust of wind blew past his face, and he squinted a little. However, the rune was not 'Air'. Jane stepped towards the rune, and tried to touch it, but his hand was blown back by some unknown energy.
"Do you see it now, my disciple?"
"What exactly am I supposed to see?"
Despite his remark, Jane could imagine a certain effect from those runes. He was yet to complete his hypothesis, though.
---
While walking home, Jane had more or less figured out the principle of the defense magic his teacher used.
'That rune... it generates a force.'
The rune which his teacher showed had the effect of physically pushing things around it. Jane decided to name it 'Force'.
'Then, what happens if I negate it?'
Jane raised his arm, then gathered mana around it. He formed a 'Negate' rune, then put a 'Force' inside of it...
"Ow, ow ow ow—!"
Immediately, the affected portion of his arm exploded in extreme pain. Jane hurriedly dispelled the magic, but the damage was already done. He could feel extensive harm having been done to the blood vessels inside.
'It's not that simple, huh? Also, ow...'
In hindsight, it was obvious what had went wrong. Since he stopped all of the forces within his arm, what would happen to the blood vessels inside? Nothing good, clearly. Jane began seriously reconsidering his lack of fear towards testing spells on his own body.
Jane walked up towards a tree, and began his second attempt. This time, he didn't put the rune inside the defended object, but instead laid it over the very surface of the bark. He also enclosed it inside of a 'Project', oriented towards the outside of the tree.
When it was complete, he formed a fist and punched the tree with all his might. As his fist impacted the surface of the tree, all of the weight within it dissipated. Neither him nor the bark of the tree was harmed. His second attempt was a success.
'Hold on. This isn't what he did.'
His teacher's defense magic did not have the same effect as Jane's attempt. For one, the earlier impact sent Calex flying, and yet caused no real damage. Additionally, even if his skin was unharmed, the speed at which he flew should have caused internal damage. Thinking of this, Jane had an idea.
He drew mana out of his core, but instead of forming runes with it, imbued it into his body. He focused mainly on his circulatory system, adding in a little extra range just to be safe. His muscles were imbued as well, although to a lesser degree. The mana would protect him from the worst of his magic's effects. With that step complete, he began forming runes.
He formed a 'Diffuse' along with an auxiliary 'Void' and 'Negate', then placed the 'Force' rune inside. The structure of the 'Void' slowly became messier, loosening it's effect on his runes. He also felt the pressure on his body increase, as well. However, it was much more bearable than before. Eventually, the 'Void' had disappeared completely, and his prototype defense magic was in full effect.
Jane walked around a bit, observing how he was affected. His body was not completely disconnected from the world, and yet he felt his steps grow softer and the air become thinner. His muscles felt slightly stiff, too.
'That cheater probably used some runes to deal with this.'
Jane walked up to the tree from earlier, and punched it with all his might. His fist recoiled a little, and he felt a slight pain flash through his bones. However, the rough surface of the tree would normally have damaged him far worse. His attempt, to an extent, was a success.
'I need to cover more of my skin, though.'
This method of defending oneself was far too weak to take a focused attack head-on. The reason why his teacher had gotten away unscathed was also partially due to his robe, which dispersed the impact. That, and he may have reduced the amount of mana imbued inside his body.
'The next time I see him... will he still look like a homeless man?'
Jane hobbled on his way back home, fighting against the rigidity of his movements. Realizing how stupid his actions were, he released the defensive magic, and began walking normally again. Suddenly, he keeled over and started vomiting up blood. Liquid began pouring from his nose and eyes, as well.
'Fuck... the strain...'
His magic had decent defensive effects, but negating the force inside his body would cause serious damage. However, protecting himself with more mana would render the spell ineffective. He had to use that magic sparingly from now on.
"Ow, ow..."
Jane clutched his stomach, and limped through the forest.