In Mushoku Tensei with an A.I. Chip

Grant's thoughts were interrupted when he suddenly felt the rapid approach of several somethings. Without sight nor sound, the Sword Saint could only rely on the faint sensations of air pushing against his skin to sense the incoming projectiles. 

He swung his sword thrice, cutting through the projectiles that dispersed upon contact with his blade. It wasn't anything sharp nor hard, making the swordsman wonder what exactly his young charge had shot at him. Unless it was only a distraction…

Behind! Grant swung back 180 degrees to preemptively stop what he assumed would be a sneak attack. But there was nothing. Completely enveloped in darkness, with not a single sound reaching his ears, having multiple sources of movement all around him and with no way to even count the time passing without relying on his internal clock… It was easy for paranoid vigilance to set in extremely quickly.

Fighting such a battle was torturous especially for a Sword Saint who specialised in frontal, direct assaults. 

Grant let out an annoyed huff. It had been a wild guess, but that wrong guess was all Luke needed to sense vulnerability and a silent gust of wind, moving through space unperturbed by friction and air resistance and thus causing no shifts and movements in the air, was shot next to his face. 

The Sword Saint could feel a sharp pain on his cheek, and with that, he annoyedly sheathed his sword. It was a wind blade that could have just as easily cut through his neck or throat, given that he couldn't even detect the incredibly stealthy spell that was aided by a lack of sight, sound and air resistance. 

"Yield." The word was becoming more detestable to utter with every time he spoke it. 

The black sphere of darkness suddenly disappeared, being drawn towards Luke extremely quickly. The boy condensed the gathered black smoke into a dense orb that was like a tennis-ball sized black ball. 

Luke then encased the black ball in a layer of something solid, capturing all of the thick, opaque black smoke that had blinded Grant throughout the fight. 

He gazed at the black ball for a moment before pocketing it with a satisfied nod. It was a spell he could reuse in the future by throwing it and shattering it on the floor, creating an instant sphere of darkness. 

As someone with a limited pool of mana, he had to find clever ways like these to preserve his magic power in future combat scenarios. All of his spells had been modified and improved to minimize mana cost. 

Mana and magic defied the laws of physics that Luke had grown up learning. Using magic, one could go against the fundamental principles of the universe and how physics functioned. But if one could marry science and magic, the resulting union would be greater than the sum of their parts. 

For instance, one of his favorite spells he had invented so far was Solar Lens. Rather than creating fire from mana, an energy inefficient process, Luke instead bent airflow and light through refraction using precise control of air density and shape to focus sunlight into a concentrated beam of heat. It was a combination of magic leveraging on physics and environmental forces to achieve greater results. 

The mechanics of the spell involved Atmospheric Lensing to alter density and temperature in air, bending and focusing sunlight and compressing its energy through refraction, micro-vortex engineering–tiny, spinning whirlpools of air compress and stabilize the refracted lens, holding the "focus point" steady even in open air. The resulting solar heat ray was like a concentrated laser. 

To ignite something like paper would take around 1 unit of magic power. Going up in temperature and intensity would proportionately increase mana cost. Generating a Solar Lens that could carve through human flesh would only take slightly less mana than the average Advanced-rank spell, but with much deadlier results. 

With the darkness cleared, Luke and the gathered audience could now see a frowning Grant with a red line on his cheek, drawing blood. 

It was an indication that Luke could have cut through his jugular instead of merely grazing his cheek had this been anything but a friendly spar. 

Any spell below Advanced rank would not have been enough to pierce the layer of Touki Grant covered himself in. The Vacuum Blade Luke shot out had been derived from an Elementary Wind spell, but with enough mana pumped in to not only raise its sharpness and speed to a level that could cut Grant's skin, it also moved through the air coated in a layer of mana that reduces air density and friction to near zero around the blade, eliminating air resistance and sound to negligible levels. 

Luke approached the sword saint. "How was it?" He asked, curious for the feedback from the person who he subjected his latest created spells. 

Grant sighed and shook his head, "Once young master took away my eyes and ears, I was left entirely passive. I could have ran out, of course, but that would have defeated the purpose of the spar. Besides, I doubt you would have let me leave the field so easily."

"It was extremely easy then, as you would have already predicted, to trick someone who cannot trust his senses. If I was kept in there longer, having to defend myself from random sneak attacks, I might have eventually gone crazy…"

"I see." Luke agreed. "Thank you for your feedback."

Grant could see Luke making the mental note to use sense deprivation in future fights based on its proven effectiveness. He shuddered to think of his future duels with the young master. 

"If you don't mind my asking," Grant hesitated for a second before continuing, "How did you know where I was? I couldn't see or hear anything, so how could you?"

Luke smiles faintly, "Mana threads spread over the ground like a spider's web. As long as your feet were touching the floor, I knew exactly where you were." 

"But you could sense where my head was from that?" Grant puzzled. 

"Lucky guess." Luke's grin widened jokingly. 

"I-I see…" 

Grant paled, realising how close he had been to a Wind Blade carving out his trachea instead of merely cutting his cheek. 

Lucky guess? Of course not. It had been a guess made with 97% accuracy based on the A.I. Chip's calculations. Echolocation through a release of a thin pulse of mana, the direction Grant's feet were facing, a thorough analysis of his stances and habits, and a dozen other factors that gave Luke the confidence to blindly cast the Vacuum Blade.

Even while 90% of its processing power was dedicated to analysing the growing database of potential potion ingredients and simulating alchemical reactions with the Six-Sided world potion ingredients, the A.I. Chip was still unparalleled in such simple calculations. 

"Woohoo! Grant you got your ass kicked! My baby won! You're so cool! Kyaaaah!!" Selena cheered from the side. 

"Madam…" Grant held back a tear while Luke helplessly shook his head in amusement. 

The eight year old then gestured towards the North Saint. 

"How about it then? Do you want to join us, Bernard." 

Said swordsman grimaced, "I don't think I can do much else against your darkness and silencing spell, young master…" 

"Don't worry. I have gathered enough data for the blind and deaf combo. I want to try out something else." Luke reassured him while sparks danced between his fingers. 

Bernard glanced at the crackling plasma fluttering around the lordling's hand, and paled before sighing in resignation, "Please promise to heal us up once you're done tormenting us, young master." 

"You make me sound like a monster," Luke replied in affront. "We're just training. Isn't that right, Grant?"

The Sword Saint nodded firmly, "Yes, young master. King-rank is within reach, I can feel it." 

That was the reason why Grant was usually the most enthusiastic of the three to train with Luke. The magician was full of trickery, but at the same time was fully capable of going head on against the Sword Saint and still win. Constant battles against an ever evolving opponent like Luke was an incredibly beneficial stimulus for any swordsmen. 

"Once you reach it, you need to go back to the Sword Sanctum don't you?" 

Grant paused before nodding in the affirmative, "Yes… Only the Sword God can make my ascension official if he witnesses and deems my mastery sufficient. That, or I defeat an existing Sword King in a duel to claim their title." 

Luke thought for a moment before remembering something. "I heard that one of the Greyrat families has taken in a Sword King as a retainer. It was House Boreas, was it not?"

"That's right. The Black Wolf Sword King Ghislaine Dedoldia." Grant answered. 

"Hoh… I wonder how they managed to swing that. Do you know her?" 

The Sword Saint's brow furrowed at the recollection, "Unfortunately, I do. We trained under Gal Farion at the same time. Though she was a beast of a woman even then."

Luke look amused, "Did she beat you up before?"

"Ugh, more than once I'm afraid. She was the type that would throw hands without even saying a word if she somehow felt slighted. She could barely speak the common tongue, so trying to talk to her wouldn't work either. In the end, the rest of the Sword God's disciples just learned to leave her alone."

"She became a Saint before me, but wasn't satisfied and challenged the Sword God almost every day even though he beat her every time. Thankfully we had healers attached to the Dojo otherwise she wouldn't have lived long enough to become King." 

Though Grant spoke nothing but negatives, he had a wistful smile. 

Luke caught it and smirked in response, "Sounds like you admire her a great deal."

"Ghislaine was undeniably talented, but she moved with the instinct of a beast more than a human. When we asked, Master said it wasn't possible for her to go beyond Saint-rank without developing human intelligence. I left the Dojo before she became human, so I suppose you can say I am curious what she is like now." Grant admitted. 

Luke nodded, satisfied with the answer. "Very well, I shall request grandfather to extend a special invitation to their family for my second birthday (10 years old) celebration. You have until then to reach the level of King, Grant. Take her title for your own." 

Grant looked taken aback, "Your second birthday, young master? That's in less than 2 years, isn't it?" 

The young noble chuckled, "Indeed. You better get to work, or she might just cut you in half instantly during your duel." 

"Y-yes!" Grant saluted stiffly. Musing about reaching King-rank was one thing, being given a hard deadline was another. A year and some change. Was it really possible? 

Perhaps a Sword God style practitioner needed precisely such pressure in order to push them to go higher, for Grant certainly looked more enthused. 

"Now the both of you, come at me." Luke ordered, rousing his magic power and circulating it internally. "This time, you're not getting off as easily as a small cut." 

Grand and Bernard looked at each other before drawing their swords. This was not the first tag team duel they've had against Luke. They've won and lost before, largely dependent on what spellset their charge was testing out that day. 

"You go left, I'll go right." Was all Grant said before he leapt into action. 

Bernard cursed silently, withdrawing three throwing knives from his hidden pockets and then running forward as well. 

Luke smiled. This was to be a head on battle. No tricks. Both for Grant's growth and his own as well.