Chapter 17
Mana backflow is a phenomenon that occurs when using advanced or powerful magic.
Mana poured into gremlins or magic stones, or held suspended in the air (for witches and wizards only), can lose control, take on the nature of the spell being cast, and flow back into the body, causing feedback damage.
For example, backflow from Freeze-type magic will freeze your body, while backflow from future-sight magic will turn your brain to mush. With eyeball magic, you'll go blind.
If the backflow is severe, the magic runs wild and kills you. Apparently, Katsushika Ward was once reduced to a wasteland because a wizard let a powerful spell run wild. The wizard supposedly burst apart and turned to dust. That's terrifying.
Witches and wizards can reduce the feedback damage caused by mana backflow by controlling their mana. They either simply push back the mana trying to flow backward or skillfully divert it and release it into the atmosphere.
But of course, mana control has its limits. Even the Blue Witch nearly let her magic run wild when freezing a giant monster, while future sight apparently damages the brain and leaves its user mentally regressed to infancy every time they look into the distant future.
The problem is ordinary human wizards who can't control mana.
Tokyo Magic University is currently struggling with this mana-backflow problem.
There are many dangerous spells that, despite being pronounceable and having sufficient mana, are effectively unusable because of mana backflow.
Fire magic is the chief offender.
The Everflame Witch's foundational fire spell, "Flame!," can be cast with very little mana and a short chant, but apparently fire magic in general is particularly prone to mana backflow.
Magic that produces fire doesn't seem all that advanced, but apparently even the simplest fire magic can melt the ice of a Grand Glacier spell that nullifies the thawing effect of ordinary fire. I guess it comes with some amazingly advanced magical bonus effect by default.
When an ordinary person uses "Flame!," mana backflow occurs easily and burns them. The spell itself can be activated, but the benefits and drawbacks don't exactly balance out.
Since this magic is attracting attention for cooking, heating, and use as fuel, Professor Ohinata has been researching ways to prevent mana backflow alongside teaching.
Just as a safety sound prevents a spell from going off accidentally, they've been trying to determine whether adding some kind of pronunciation or word to the chant can nullify or reduce mana backflow, but apparently without much success.
According to Professor Ohinata, the fuel problem isn't as urgent as the food problem, but it apparently ranks high in priority.
Ideally, being able to research healing magic would be the top priority after food, but no healing-magic users exist, so there's no way to conduct research. As a result, the fuel problem has been moved up the priority list.
At present, central Tokyo mainly uses lumber obtained by dismantling unoccupied buildings to provide fuel for cooking and winter heating. But no matter how carefully that downtown lumber is conserved, it will eventually run out, and even if trees are planted, it will take ten to twenty years for them to grow large enough to use as fuel.
Logging in the mountainous areas on the outskirts and transporting the timber to the cities would also require a tremendous amount of labor. Charcoal-powered freight trains are expected to help with that kind of transport, but the fuel for those charcoal trains is, when you trace it back to the source, wood. It deserves praise as the product of wonderful technology, but unfortunately it can't be called an efficient means of transport.
Magic, after all.
Magic solves everything.
The foundational fire spell "Flame!" continues burning in place for several minutes unless you swing a wand and launch it. That's more than enough for simple cooking, starting a fire, boiling water, or reheating prepared food.
Apparently, about one person in three has enough mana to chant this spell, so if things go well, having one fire mage per household isn't just a dream. Taken across all of Tokyo, it would result in incredible fuel savings.
If we can't get fire magic into usable condition, the plan is apparently to work on improving and popularizing charcoal freight cars, as well as transporting lumber from the mountains by water. So this isn't someone else's problem for me, either.
After all, the Tama River flows through Okutama in the mountains, runs through Tokyo's urban center, and empties into Tokyo Bay. It's an ideal river for waterborne transport.
If I take it easy, hordes of forestry workers will descend on Okutama and start noisily cutting down trees in my peaceful home. There's even a risk they'll build a logging base there.
I hate that idea far too much.
Professor Ohinata's letter was filled with considerate phrases like "if you have the time," "there's no deadline," and "work at your own pace, Orito-san," but despite that, the professor's explanations of mana backflow, the progress of the magical-linguistics research, and the problems they had encountered were written in painstaking detail and with considerable passion.
The letter made it clear in places that the professor was quite stuck, so I decided to put in a little extra effort and lend a hand.
Even though the magical-linguistics approach had reached a dead end, the problem might be fairly easy to solve from the processing-engineering side.
First, after delivering the letter, I asked the Blue Witch for her thoughts on mana backflow while she built a deck with a card box on her lap and I read the letter carefully.
I only know the phenomenon of mana backflow in theory. I wanted to hear the opinion of a witch who had actually experienced mana backflow and possessed some ability to control it.
When I showed Professor Ohinata's letter to the Blue Witch and asked her opinion, she gave me supplementary details that only a witch who had actually experienced and dealt with mana backflow could provide.
"You can really feel it when using magic with Curanos, but there is actually a way to hold a wand that makes mana backflow less likely."
"Huh? There's a way?"
"There is. Hold it like this... No, would it be easier to understand if I drew it?"
The Blue Witch held Curanos and tried to explain, but then changed her mind and drew two comparative diagrams on a sheet of paper.
"What are you, a stick-figure artist?"
"Ugh... I-I can't help it! There are girls who are bad at drawing, too. Ahem, anyway! First, the one on the left is the bad way to hold it. When you use magic, mana is released from your mouth along with your voice and poured into the magic stone. When mana flows backward, it enters the part of the body closest to the magic stone. In the diagram on the left, the closest part is your head, right? The mana flows directly into your head, which is dangerous, and it also makes the backflowing mana difficult to control."
"Hmm... So if I held the magic stone between my toes, the backflowing mana would flow in through my toes?"
"That's right. Now look at the diagram on the right. This is the good way to hold it. The closest part to the magic stone is the tip of your right hand, so the backflowing mana flows from your right fingertips through the rest of your body. It's far safer than having it flow straight into your head, and the backflowing mana is easier to control, too."
"I see..."
So the route for pouring mana into a magic stone or gremlin and the route for mana backflow are different?
Following that logic...
No...
It might work... maybe...
It seems theoretically possible. I should ask her.
"Hey, do you think mana backflow could be reduced if I made the red section resistant to mana, like this? You can answer based on your gut feeling."
I quickly drew a simple diagram and showed it to the Blue Witch.
"Wow, how can you draw such an accurate circle freehand? Wait, you're a stick-figure artist too, Orito."
"What's wrong with that? I can draw photorealistic pictures as well as photographs. It's fine to take shortcuts when you can. Anyway, what do you think? Mana is sent along the black-arrow route and flows back along the red-arrow route, right? I think we could use a mana-resistant material in the shaft of the wand between the magic stone and the right hand."
"...Hmm? I'm not quite sure what you're trying to say."
"Is it hard to understand? The other day, we melted a gremlin and solidified it in that experiment, remember? The one with the reverberatory furnace. I think I mentioned it before, but if you put that between a gremlin and yourself, the amount of mana a spell consumes doubles. In other words, it causes a 50% loss of mana."
"If I use melted-and-re-solidified gremlin in the red part of the wand's shaft shown in this diagram, the mana flowing back will be cut by 50%! Half the backflow mana! Half the feedback damage! That's what I figure, anyway. What do you think?"
"..."
The Blue Witch rested a hand against her chin and thought for a while. Then she pressed Curanos against the paper covered in her doodles and chanted a spell.
"Moonshadow and cool breeze, too—let everything become ice!"
After transforming the paper into a thin sheet of ice, the Blue Witch flexed her fingers as if checking the sensation, then nodded.
"Yes. If the red line in that diagram is difficult for mana to pass through... if it causes mana loss, then using it as a material feels like it would reduce the amount of backflowing mana."
"Oh! Really? I had a feeling that was the case! Ha-ha!"
The melted-and-re-solidified gremlin I'd thought was a completely useless piece of shelved research looked like it might actually be useful, which made me laugh. By the time the research became necessary, it had already been completed.
As expected of a genius. I really am the world's greatest wandmaker...!
This was a solution I came up with in seconds based on the research of Professor Ohinata and the unnamed team that conducted the gremlin-melting experiments, so it wasn't all thanks to my genius. Still, even I was trembling at the power of my own ideas.
Taking useless experimental data and finding a way to use it—that's how a first-rate engineer uses his brain! My inspiration is on a different level from all those run-of-the-mill creators. Inspiration, I mean.
I immediately began modifying Curanos based on the theory I'd devised.
I disassembled Curanos, shaved down the shaft, made a long, narrow cavity inside it, and fitted in some melted-and-re-solidified gremlin.
I asked the Blue Witch to test it for mana backflow, but Prototype One failed. The backflowing mana didn't pass through the melted-and-re-solidified gremlin; it went around it and flowed straight into her hand.
By feel, the Blue Witch said there was a gap between the melted-and-re-solidified gremlin and the magic stone, allowing the backflowing mana to leak out. She thought it would flow as intended if I created a point of contact, so I made the requested improvement and had her test Prototype Two.
Prototype Two succeeded without a hitch, but the mana-backflow reduction rate remained around 50 percent, just as theory predicted, as far as the Blue Witch could tell.
That was a tremendous result for only two prototypes. If I reported this theory to Professor Ohinata, she'd be delighted that the problem had been solved so quickly.
But it doesn't end here. I'm not done yet! I can raise the mana-backflow reduction rate even further!
If one melted-and-re-solidified gremlin doubles mana consumption and cuts backflow by 50 percent, then four of them would double mana consumption another two times, and then another two times, and then another two times. Two to the fourth power is sixteen! That means an astonishing 93.75 percent reduction in backflow mana!
That's what I thought, anyway, but even when I bundled four rod-shaped pieces of melted-and-re-solidified gremlin together inside the shaft, the reduction rate only reached about 85 percent.
I also tried bundles of five and six, but according to the Blue Witch, "I can't tell that anything changed."
Even reducing it to a bundle of three left the reduction rate at around 85 percent, while a bundle of two brought it down to about 75 percent.
In other words, mana-backflow reduction using melted-and-re-solidified gremlin tops out at 85 percent.
It seems like I could push it a little further, but I can't think of any better processing ideas right now, so I'll call this finished for the time being.
I wrote to Professor Ohinata, "I've figured out how to apply anti-backflow processing!" and took the opportunity to request a recall of the standard wands used at Tokyo Magic University.
I want to collect them all for the time being and replace their shafts with ones fitted with anti-backflow mechanisms.
The replacement work will be a hassle, but if a mana-backflow accident occurred with one of my wands, I wouldn't want it to look as though my wand was to blame.
Rather than hear, "I used a wand, but it couldn't prevent a mana-backflow accident," I want praise like, "Thanks to the wand, we prevented a mana-backflow accident, I got a girlfriend, became a regular on my club team, and my grades went up! It's all thanks to the wand!" Please make sure to give it a ☆5 review.
Professor Ohinata accepted the recall, immediately collected the standard wands, and had them delivered to the Blue Witch along with a personal thank-you letter and a letter of appreciation from Tokyo Magic University. The professor heaped praise on me for solving the problem in one day. It was embarrassing.
Actually, Professor Ohinata, who improved Harvest magic and undid my transformation in a single day, deserves plenty of credit too. Neither of us technically did it in a single day, since our lightning-fast solutions were built on years of foundational research. Still, let's keep complimenting each other freely.
I saw tremendous potential in the new version of the wand, which had evolved after Professor Ohinata assigned me the problem and the Blue Witch served as its tester.
Until now, the only meaningful parts of the wands I made were their core magic stones or gremlins.
Frankly, all you had to do was hold a processed magic stone directly. The shaft and engravings were nothing more than decorative flourishes.
But now the shaft of a wand had finally acquired a proper function.
The jewel at the tip, which serves as the core, amplifies the magic, while the shaft reduces feedback damage.
Isn't this a beautiful structural collaboration?
If I continue my research, I might be able to give proper magical functions to the protective material around the jewel, the metal used to strengthen the shaft, and even the engravings on the shaft. The possibilities are endless.
There is still plenty of room to improve magic wands. Let's keep evolving them.