The assembly process was also extremely easy, just arrange the parts properly then fix them in place with pins. The pins were secured using simple glue. Once the pieces were in place, they checked every movement to make sure nothing could bind or have any instant issues. Issues cropping up later didn't matter, at the moment. When it was done, they had a fully articulating wooden arm in just over two hours of work.
With the assembly of the arm complete and it now counting as 'one item' for the purposes of his enchantments, it was time to do the actual hard part. Though Azazel had been very helpful with the work involving the machines and such during the process of shaping the arm, this was the part Junichiro really wanted him for.
Junichiro picked up a thin calligraphy brush and dipped it into some regular ink, "Pay close attention Azazel. Once I finish drawing out each rune, I will need you to use the chisels to carefully carve them out. You must carve them in the exact same way I draw them out matching me stroke for stroke."
Azazel nodded seriously and even felt a little excited to see the kid at work. Junichiro stared hard at Azazel, "Once they're carved out, they need to be filled with gold." He lifted up a spool of golden wire he'd made back at his old haunt, "The gold needs to be placed the same way and gently hammered into place, I'll do that. So, pay very close attention so you don't make a mistake. I'll keep watch as well and interrupt if you're about to do something wrong."
Azazel chuckled, "Don't worry kid, my memory is pretty good. I wont make a mistake."
Junichiro just eyed him for a bit before huffing and getting to work. This was the part that he truly needed Azazel's help for. Junichiro was a fair bit stronger than he had been just six months ago, but it was nowhere near strong enough for what he needed. In order to make a prosthetic like he was picturing, he needed to use mid or high tier runes. He'd never be able to do the initial power up on such runes by himself. They required an initialization cost but, with the right sequence, could then draw mana from the atmosphere and keep working for as long as possible.
It was only once he had the ability to do these types of permanent mid-tier enchantments on his own that he could consider himself a Journeyman Artificer. That was still a fair bit into the future, but by havinng Azazel carve, place, and power the runes, he would be able to make a much more functional replacement limb that wouldn't constantly require him to power it with his own mana reserves. Additionally, it would take significantly fewer runes to achieve the same results. Higher tiers were simply took more power to initialize, then became more efficient and powerful in their effect. The punishment for making a mistake with them was equally powerful.
Working one rune at a time, Junichiro would use the calligraphy brush to write out the rune in the proper fashion on the proper spot on the arm. Once it was finished, Azazel would carefully carve the channel for the gold in the exact same way. With the channel finished, Junichiro would place the golden wire within it, then used a summoned hammer to gently set the gold in place. Gently hammering the gold caused it to spread out and locked it into place within the wood. It also allowed Junichiro to channel his mana through the gold and mark it with his personal signature. While not strictly necessary, it would help with the operation of the arm later.
With Azazel's help, the project advanced rapidly. While Junichiro was skilled and knowledgeable, Azazel was in an entirely different skill level. Work that would have taken Junichiro many hours as he carefully took his time to prevent mistakes, took Azazel minutes. Azazel didn't even need to use the hammer with the chisel, he just used his own strength and easily carved through the wood with laser-like precision. Junichiro was honestly a bit jealous of the skill Azazel displayed. He'd reach that realm of skill eventually!
Within seven hours, construction of the arm was finished. They'd even attached a harness to strap the prosthetic over his shoulder and across his chest to keep it firmly in place. Junichiro almost wished he'd decided to make a more complex arm thanks to all the time and effort having Azazel help out saved. Their creation was crude at best, but was going to be functional and that's all Junichiro had been aiming for. With a functional replacement he could work on something better as an upgrade, then something better, and so on. After all, Mana Steel was the bare minimum of magical metals so it wouldn't be used for his final creation.
After triple checking all of the runes on the wooden arm, Junichiro turned to Azazel, "It looks fine. For the final step I need you to touch this rune..." He pointed out the very first rune that had been carved, "And channel magical energy into it until all of the runes on the arm completely light up. Once that's done, I can test it out."
The first rune in the scheme was for the absorption of mana. It was technically already glowing, but the glow was so weak that they would need to be in a pitch black room to see it.
It had been absorbing mana since it was created several hours ago and, if left alone, it would eventually absorb enough mana to power the arm. However, that would likely take years. Having Azazel 'jump start' the process would speed things up drastically. Once everything was initialized, the energy consumption of the arm would drop drastically and only really change as he was using it. A change that he could easily compensate for with his own mana if necessary.
Otherwise the natural regeneration from the rune should be enough to keep it running. A self charging battery essentially.
Azazel did as asked and placed the tip of his finger on the rune before channeling his power into it. He cocked an eyebrow as the arm greedily drank in power, "Huh. I didn't expect it to cost this much energy."
By the time he was done, several minutes later, both of his eyebrows had risen, "That took, roughly, the same amount of energy I would expect a four-winged angel to possess. Quite the greedy set of runes you chose."
The way Azazel was looking at him left no doubt that he was asking Junichiro about the runes. In response, Junichiro just shrugged his shoulders, "I used the best set I could with the medium I had available. I wouldn't be able to power it myself anytime soon and wouldn't have used it without you here. If I was alone, I would have had to use a lower tier scheme which would require dozens more runes and time. This saves effort and time, both priceless things."