A Complicated Simple Solution
As Jien failed once again to cast a wind elemental spell to manipulate his rapier from one hand to another, he had a thought, a slightly terrifying thought. His blade was knocked away before it swapped hands and though he was able to get it back under his control it was not before Mark had his blade pointing at Jien's throat.
The thought was simple. If he wanted a blade that could act autonomously why not breathe a semblance of life into it. If it could act for itself and was able to act in the way Jien needed, then wouldn't he be able to work as one with his sword to outmaneuver his opponent.
The trouble came in how to act upon the thought. It wasn't impossible to imbue life into objects. Types of magic that could create golems or other artificial life forms did exist. The only issue is that generally these techniques were only short term. Once the imbued mana in the spell or the mana of the resource used as a power source was used up the artificial life form would stop functioning. He would have to find a way around this, and that was definitely above his level of knowledge.
There were slightly darker paths, though some would call them evil. One could complete blood rituals, soul rituals, necromantic rituals and the like. These may make such a weapon, but the variety of negatives was a wide as the ocean. At the end of the day, you would be dealing with something more than a little sentient. Even if you bound the blade properly the chances of you dying it were still rather high. Neither Jien, his mentors, nor his father would allow such a risk.
This left a bit of a conundrum to the solution. How to create a living blade without it not actually being alive and sentient on the level of an animal or human. Jien continued to mull the thought over as he continued to train and slowly absorb the information from the alchemy guide.
It was as he was looking through the alchemy book that the idea came to him. He was reading description for a particular type of plant called Serpent Vine. The plant itself was just as its name described. It was a vine that would act like a serpent when in the vicinity of other living beings. It was a man-eating plant of sorts that would coil around its victim before unveiling poison laden thorns that would be hidden within its foliage. After the victim would perish the vine would mulch the body using its thorns as blades and use it as fertilizer to grow and expand its territory.
His thought was simply to find a way to link something like the Serpent Vine to his sword and use it to control it in a semi-autonomous fashion. The plant was alive most definitely, like all flora, but it lacked the level of intelligence to become an inherent danger liking fusing the soul of an animal, magic beast or even worse a person would. The issue then lay in how to control the plant properly and avoid become its fertilizer, though there could be something said if he could retain some of the Serpent Vine's reacting to living beings and focus it to only those that he deemed fit.
There was also the issue of how best to fuse a living plant into an enchanted blade, but that would likely be an issue to resolve if he could figure out the solution to the first issue. To figure out the solution to the first problem of controlling the plant and being able to use it he started to research the Serpent Vine and other plants along the same line. Unfortunately, the manor library did not have a large number of books on plat life. The few that he did find were about more ordinary house plants or flowers with no particular special properties.
This ultimately led Jien back to discussing it with his mentors, the result of which was much as it had been earlier on in the project, at least in the case of Emily. The fencing instructor was left with her jaw hanging open once again in shock. She was constantly questioning her sanity at the suggestions that Jien had come up with. It was like he was taking the fencing style passed down to her and turning it into a magical experiment.
If he succeeded in the addition he wanted to make, she questioned if he would ever be able to actually pass it down to another student. Even if he could pass it down, would it even be considered a style of fencing anymore? Would it be something entirely different at that point? She didn't have answers to those questions. All she could do was smile somewhat bitterly and nod her head stiffly, trying to give Jien some general guidance since his thoughts were vastly out of her expertise.
Mark on the other hand felt that the thought was ingenious in its own unique way. The issue was in execution since there were a few different paths that were possible. Mark may not have been a master in the study of magical plants, but he was decent enough to point Jien toward a few different possibilities.
The first of the possibilities was to splice the Serpent Vine with a less lethal plant and then bind it with a spell to Jien's rapier. If he bound it as a seed and then used a variety of magical means to control the plants' growth to be symbiotic with the sword it could work. Likewise, Jien could use formations to forcefully bind a Serpent Vine to the blade and install instructions within the formation. The formation would use the plant as its power source thus alleviating the issue of the power source's life span. The final solution he could think of was to forge a new blade entirely and use the vine as an ingredient in the forging process, much like a piece of ore. If done correctly and with precision the vine would then no longer be a separate entity from the sword, giving the sword itself a simile of life.