Chapter 17: Magic backflow prevention mechanism

Magic backflow is a phenomenon that occurs when using advanced or powerful magic.

It happens when magic power, whether poured into a gremlin, a magic stone, or suspended in mid-air (for witches and wizards), becomes unmanageable and flows back into the caster’s body, taking on the properties of the spell and causing feedback damage.

For instance, if magic backflow occurs with a freezing spell from the Vaalar line, the caster’s body freezes. With a foresight spell, the caster’s brain gets fried. With an eye-based spell, it results in blindness.

In severe cases, magic can go berserk, leading to death. There’s even a story that Katsushika Ward was leveled when a wizard lost control of a powerful spell. The wizard, apparently, was blown to smithereens and reduced to dust. Terrifying.

Witches and wizards can mitigate feedback damage from magic backflow by controlling their magic power. They can either push back the backflowing magic or skillfully divert it into the atmosphere.

However, even magic control has its limits. The Blue Witch, for example, almost lost control when freezing a colossal monster, and foresight magic reportedly damages the brain so severely when seeing far into the future that it causes the caster to regress into a childlike state.

The real issue lies with ordinary human wizards who cannot control magic power.

At Tokyo Magic University, the magic backflow problem is currently a significant challenge.

Even if a spell is pronounceable and the caster has sufficient magic power, many spells remain practically unusable because of the danger posed by magic backflow.

The prime example of this is fire magic.

The core spell of fire magic, “Blaze, Jin-Ga,” from the Witch of the Eternal Flame, is relatively low-cost and has a short incantation, but fire magic, in general, is prone to causing magic reflux.

Fire magic doesn’t seem particularly advanced, but even the simplest fire spell can melt the ice of a great glacial magic spell, which nullifies physical fire defrosting. This likely means that fire magic has some inherently high-level magical effects by default.

When an ordinary person uses Blaze, Jin-Ga, it frequently causes magic backflow, resulting in burns. While the magic itself can be activated, the risks far outweigh the benefits.

This is particularly problematic since fire magic is highly valued for its potential applications in cooking, heating, and as a substitute for fuel.

Ōhinata-sensei has been working on anti-magic backflow research alongside her teaching duties. She’s experimenting with adding certain pronunciations or keywords to the incantation to prevent or reduce magic backflow, much like how safety tones prevent explosions. However, she hasn’t made significant progress yet.

According to Ōhinata-sensei, while the fuel problem isn’t as urgent as the food crisis, it remains a high-priority issue.

Ideally, research on medical magic would take precedence after addressing food supply concerns, but since there are no practitioners of medical magic, it’s impossible to study, leaving the fuel problem as the next priority.

Currently, urban areas primarily rely on wood sourced from dismantled uninhabited buildings for fuel, used for cooking and winter heating. However, no matter how frugally this wood is used, it will eventually run out. Reforestation efforts won’t yield usable trees for fuel until 10 to 20 years later.

Harvesting timber from mountainous areas and transporting it to urban centers is also labor-intensive. While charcoal freight trains are expected to assist with such transportation, the fuel for those trains ultimately comes from wood as well. While it’s a marvel of engineering, it’s far from an efficient solution.

Ultimately, magic is the key. Magic can solve everything.

The core fire magic spell, Blaze, Jin-Ga, burns in place for several minutes unless launched with a staff. It’s sufficient for small-scale tasks like cooking, igniting fires, boiling water, or reheating food.

Roughly one in three people have enough magic power to cast this spell, meaning that with proper utilization, the dream of having one fire magic user per household could become a reality. On a citywide scale, this could significantly reduce fuel consumption.

If fire magic cannot be made safe to use, plans to improve and expand the use of charcoal freight cars or water transportation for timber from mountainous areas will move forward. This issue isn’t someone else’s problem for me either.

After all, in the mountainous area of Okutama where I live, the Tama River flows directly into Tokyo’s urban areas and eventually the Tokyo Bay, making it an excellent waterway.

If I stay idle, forestry workers might flood into Okutama, turning my peaceful refuge into a bustling logging site. They could even build logging bases here.

That would be absolutely unbearable.

Ōhinata-sensei’s letter was filled with considerate phrases like “if you have time,” “there’s no deadline,” and “at your own pace, Dairi-san,” but despite that, it was packed with detailed, passionate explanations about magic backflow, the progress of magic linguistics research, and the issues they’re facing.

From the tone and content, it was clear they had hit quite the dead end, which motivated me to step up and lend a hand.

Even if they’re stuck approaching it from the perspective of magic linguistics, it might actually be much easier to solve through the lens of applied magic engineering.

First, while I was reading through the letter after delivering it, I turned to the Blue Witch, who was sitting nearby with a card box on her lap, assembling a deck. I decided to ask her thoughts on magic reflux.

I only know about the phenomenon of magic backflow in theory. But as someone who has experienced it firsthand and possesses some degree of control over it, I thought her insight would be invaluable.

When I showed the Blue Witch Professor Ōhinata-sensei’s letter and asked for her opinion, she gave me additional explanations that only someone who has personally dealt with magic backflow could provide.

“When I use magic with Kyanos, I can really feel it. But there’s actually a specific way to hold the staff that makes it less likely to trigger magic reflux.” 

“Wait, really? That’s a thing?”

 I asked, surprised.

“Yeah, there is. You hold it like this… Actually, maybe it’s easier if I draw it out?”

The Blue Witch started to demonstrate the proper stance with Kyanos but reconsidered and decided to sketch two comparison diagrams on paper instead.

“Stick figures, really?”

“W-well… I can’t help it! Some girls are just bad at drawing. Ahem, anyway! First, on the left is the bad stance. When you use magic, the mana is released from your mouth along with your voice and directed into the magic stone. If the mana backflows, it will flow into the part of the body closest to the magic stone. In the left diagram, the head is the closest to the stone, right? That means the backflowing mana goes straight into the head, which is dangerous and makes it harder to control the reversed mana.”

“I see… So, if you were holding the magic stone with your toes, the backflowing mana would enter through your toes instead?”

“Exactly. Now, look at the diagram on the right. This is the correct stance. In this case, the closest point to the magic stone is the tip of the right hand, so the backflowing mana flows in from the tip of the hand and spreads through the body. That’s much safer than having it go directly into your head, and it’s also easier to control.”

“Interesting…”

The path that mana takes when it’s directed into a magic stone or a gremlin is different from the path it takes during a backflow, huh?

By that logic…

Could it work…?

Theoretically, it seems plausible. Let’s ask.

“Hey, do you think adding mana resistance to the red areas like this would help reduce the backflow? Just answer based on your gut feeling.”

I casually sketched a simple diagram and showed it to the Blue Witch.

“Wow, how can you draw such a perfect circle freehand? Also, aren’t you just using stick figures too?”

“What’s the problem? If I wanted to, I could draw something photorealistic. It’s fine to cut corners when you can. So, what do you think? Mana flows along the black arrow route, and when it backflows, it follows the red arrow route, right? I think we can use a mana-resistant material for the red part of the wand’s handle between the magic stone and the right hand.”

“Hmm? Wait, what exactly do you mean?”

“Is it unclear? Remember the experiment where we melted down a gremlin and solidified it? The one with the furnace—I think I’ve mentioned it before. When we put that material between ourselves and the gremlin, the mana cost of magic doubled. In other words, there was a 50% mana loss. If we use remelted and resolidified gremlin material for the red part of the wand’s handle in this diagram, it should cut the backflowing mana by 50%! That’s a 50% reduction in backflowing mana and feedback damage! What do you think?”

“…Hmm.”

The Blue Witch put a hand to her chin, thinking for a while, then placed her Kyanos staff against the paper she had doodled on and began chanting a spell.

“Moonshadow, breeze of serenity, become ice… Vaalar!”

She transformed the paper into a thin sheet of ice, then squeezed her hand a few times as if testing her senses and nodded.

“I see. If the red line in this diagram is made of material that resists mana flow—or causes mana loss—it feels like it could reduce the backflow.”

“Ha! I knew it! That’s exactly what I thought! Haha!”

I couldn’t help but laugh at how this seemingly useless research on remelted and resolidified gremlins turned out to be so helpful. By the time a need arose for this research, I’d already finished it.

What can I say? I’m a genius. I really am the world’s greatest staff maker!

While it’s true that this solution builds on Ōhinata-sensei’s work and the findings of the gremlin melting experiment team, I’m still amazed at my own creativity.

Using otherwise useless experimental data to solve a problem? That’s what top-tier engineers do! My flashes of insight are on a whole different level from those run-of-the-mill creators out there.

Without delay, I got to work on modifying the Kyanos based on my theory.

I disassembled the staff, carved out the handle to create a long, narrow cavity inside, and inserted the remelted and resolidified gremlin material.

When I asked the Blue Witch to test for mana backflow, the first prototype failed. The backflowing mana bypassed the gremlin material entirely and flowed directly into her hand.

According to her, there was a gap between the gremlin material and the magic stone, allowing the backflow to leak through. She suggested creating a point of contact, so I made the necessary adjustments and handed her the second prototype.

The second prototype worked. As predicted, the backflowing mana was reduced by about 50% (based on her sense of it).

Achieving such great results after just two prototypes was a huge success. Reporting this theory and its results to Ōhinata-sensei will no doubt make her ecstatic at how quickly the problem was solved.

But I’m not stopping here. I can do better! I can reduce the backflow even further!

If one piece of remelted and resolidified gremlin material cuts mana consumption by half (50%), using four pieces should double the doubling—2x2x2x2—resulting in 16x mana consumption, reducing backflow by a staggering 93.75%!

Or so I thought.

When I bundled four pieces of the gremlin material into the handle, the backflow reduction topped out at around 85%.

I tried bundling five and six pieces, but according to the Blue Witch, “It doesn’t feel any different.”

Even when reduced to three pieces, the reduction stayed at 85%. With two pieces, it dropped to about 75%.

In other words, using this material for mana backflow reduction seems to cap out at 85%.

It feels like there’s still room for improvement, but I can’t think of any better processing ideas at the moment, so I’ll call this complete for now.

I sent a letter to Ōhinata-sensei reporting, “I’ve figured out how to prevent mana backflow!” and offered to recall the general-purpose wands used at Tokyo Magic University.

I plan to collect all of them and retrofit the handles with the backflow prevention mechanism.

Retrofits are a hassle, but if a mana backflow accident were to happen with one of my magic staff, it’d feel like my staff was to blame, and I don’t want that.

Instead of hearing, “I used the staff, but it didn’t prevent a mana backflow accident,” I want to hear glowing praise like, “Thanks to the staff, I avoided a mana backflow accident, got a girlfriend, became a regular in my club activities, and my grades went up! It’s all thanks to the staff!” Please give it a 5-star review while you’re at it.

Ōhinata-sensei quickly accepted the recall, promptly retrieved the general-purpose magic staff, and even sent a personal thank-you letter alongside a formal certificate of appreciation from Tokyo Magic University, delivered via the Blue Witch. She lavished me with praise for solving the issue in just one day, which honestly made me blush.

But, honestly, Sensei, your own one-day feats—improving fertility magic and undoing your transformation—are no small potatoes either. Sure, these ultra-fast solutions are only possible because of a solid foundation of basic research, so technically, neither of us accomplished it entirely in one day. But hey, let’s just pat each other on the back without overthinking it.

The challenge from Ōhinata-sensei and the Blue Witch’s testing of my new staff version revealed immense potential for further development.

Up until now, the staff I made only held meaning in the core elements, like the magic stones or gremlins embedded in them. To be frank, you could just hold a processed magic stone directly in your hand. The handles and carvings were nothing more than stylish decorations.

But now, the staff’s handle has gained a real, functional role.

The gemstone tip amplifies magic, while the handle reduces feedback damage. Isn’t that a beautiful structural collaboration?

With further research, I might even be able to assign magic functions to things like protective materials for the gemstone, the strength-enhancing metals for the handle, or the carvings etched into it. The possibilities are endless!

There’s still so much room for improvement in magic wands. I’m going to keep evolving them.

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