The Demon's Apprentice || Rewrite

Curiosity

Several weeks had passed since the interaction wiht Muzan. A new routine had formed for Kokushibo, one that was both familiar and unfamiliar.

He still found himself training and consuming human flesh, elements intimately woven into his everyday life. The familiar part.

But now there was an unfamiliar aspect too. He was no longer alone. The training now focused on Tanjirou, less about his own strenght and more about guiding the young demon.

Kokushibo spent less time swinging his sword aimlessly. Instead, he found himself teaching Tanjirou the nuances of wielding a sword- the correct stances, angles, techniques, the right amount of strenght to use in a certain situation.

And when Kokushibo hunted, he didn't only think of himself and his hunger. He kept Tanjirou's hunger in mind as well.

In some ways, the new routine was refreshing. There was a tranquility in the old routine, but teaching Tanjirou, sharing his knowledge with someone so eager to learn... It brought a little more color into Kokushibo's rather monotous life.

Kokushibo remembered his days as a human, how his comraders would collapse in exhaustion and take a long time to recover. But Tanjirou was different. He showed clear signs of fatigue during every training session, yet he never stopped to catch his breath. The boy pushed on, pouring every ounce of his strenght he had into each movement, all the while sporting an excited smile.

"Your stance... is a bit off." Kokushibo said and took a step closer.

Tanjirou lowered the wooden sword, that they definitely did not steal, and watched as Kokushibo showed the correct stance, and then tried to mirror it. "Like this?"

"Almost." Kokushibo corrected the young demon's stance. "Your right... foot should be... a bit more... forward. Yes, like that... And tilt... your blade... a bit more to... the left. There. Now try... to swing... your sword again."

Kokushibo observed closely as Tanjirou raised the wooden sword and tried once more. He observed his adjusted form and the swing. There was a noticable improvement. The stance was correct, and he didn't need to exert as much strenght as before.

Kokushibo nodded once in silent acknowledgement. "Better." She said simply.

The Upper Moon looked at the hint of joy on Tanjirou's face. The young demon's eagerness to learn was a sight to see. Even with such a minor adjustement, Tanjirou was elated from getting it right this time.

Kokushibo had been right. When the Upper Moon first met Tanjirou, he had noticed a hint of talent in the inexperienced way the boy swung his nichirin blade. It was still there, under all that lack of experience. Kokushibo simply needed to continue to cut and carve and burn at it until the layered inexperience was gone, giving way to the talent and potential.

"Again." Kokushibo ordered. Despite the feeling satisfaction his voice remained steady. "Keep repeating... it until it becomes... a second nature."

Kokushibo observed as Tanjirou swung the sword, With each swing the movements became less clumsy and fluid. Progress was visible.

Then, maybe around the 20th or 23th swing, something changed. Not about Tanjirou or his stance, but about the sword. From the part where Tanjirou gripped the wooden sword, flesh started to crawl up the blade's lenght. It quickly spread, covering the entire sword in flesh.

Kokushibo watched closely while Tanjirou remains oblivious, too focused on swing the sword to inspect it closely. It seemed that Tanjirou's Blood Demon Art was manifesting for the first time.

The moment Tanjirou brought the word down on the next slice, a sharp spray of blood shot from ther blade and hit the wall with a splatter.

Tanjirou paused, noticing the sword now being covered in flesh. The moment he dropped his stance, the flesh withdrew.

It seemed that the flesh and blood had been Tanjirou's own. From what Kokushibo gathered in a quick moment, it seemed that Tanjirou's Blood Demon Art allowed him to create weapons from his flesh and produce blood prohectiles.

"Interesting..." Kokushibo mused aloud. His own sword was made from his flesh, and from what he knew, Upper Moon 6's Blood Demon Art allowed him to send poison projectiles at opponenets. It was interesting to see that Tanjirou's Blood Demon Art was taking the characteristics of the Blood Demon Arts Upper Moons had.

Tanjirou lifted his gaze from the now normal wooden blade to the blood splatter on the wall. For a moment Tanjirou simply stared. Then the boy raised his hand and snapped his fist shut. The moment Tanjirou's fist closed, the blood splatter violently exploded into flames, burning for a moment before dying out, leaving a scorched mark on the wall.

Tanjirou blinked in surprise, clearly not expecting for the blood to explode into flames. The young demon turned to look at Kokushibo. "Was that... a Blood Demon Art, sensei?" Tanjirou asked.

"Indeed, it was." Kokushibo nodded. "What you... just used was... your Blood Demon Art."

Kokushibo hasn't seen this kind of Blood Demon Art before. The ability to set one's blood on fire... A flicker of interest flashed in Kokushibo's eyes. Fire. How...

Fitting.

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The credits of the idea for Tanjirou's Blood Demon Art goes to: Robby5428

Thank you for the wonderful suggestion, Tanjirou's Blood Demon Art in the old book was a bit weird, so your suggestion was really helpful and made a lot more sense when taking Tanjirou's character into consideration :D