Chapter 155: Let me tell you about Domains.

The simultaneous use of two Domains.

For me, it was nothing short of a revelation.

If one makes you strong, then two should make you stronger. It’s a simple truth. Obvious, even. And yet, until I raced against President Rudolf, the thought had never once crossed my mind.

But in hindsight, that’s only natural.

A Domain is, in essence, a finishing move—the ultimate strike you unleash at the very end, wringing out every last drop of spirit. Normally, something like that is decisive. One hit. Certain victory. You stake everything on that final blow, so by its very nature, there is no need for a second.

I doubt I was the only one who thought that way. That’s precisely why even the brilliantly talented Teio never attempted to deploy two Domains simultaneously. It’s the common sense of racing Uma Musume—the unspoken rule.

Which is why Symboli Rudolf’s simultaneous deployment was a paradigm shift. An act that overturned conventional wisdom and opened up an entirely new horizon.

And if that’s the case, then as one of the strongest active racers, I can hardly afford not to follow in her footsteps.

"With that in mind, I did a little practicing. Simultaneous Domain deployment."

Two days after the mock race with President Rudolf, I reported the results to my trainer first thing in the morning in his office.

He was seated at his desk, stamping documents. When he stopped and looked up at me, our eyes met—those cool, composed eyes—and my heart skipped a beat.

Ugh… we’ve known each other for so long, and I still can’t handle moments like this. Is this what it means to be hopeless in love?

That said, even someone as pathetically weak to romance as me has built up some resistance over the years. At the very least, I can now manage not to look away immediately when our eyes meet like this.

Hmm. I can feel my growth. Maybe I’m not hopeless anymore. Maybe I’ve reached intermediate level. Heck, I might even be stepping into advanced territory. Just one step away from Love Master.

…While I was floating away with those ridiculous thoughts, Ayumu-san spoke.

"So that’s why you suddenly said you wanted to train with Bourbon. I was wondering. So? How did it go? Did you grasp anything?"

Ah. Right. Domains.

Since I was just about at my limit for sustained eye contact, I subtly shifted my gaze and returned to the topic.

Had I grasped anything about simultaneous deployment? Of course I had.

"Yes. I succeeded in deploying two at the same time."

"I see. Well, don’t be discouraged—…hm?"

Ayumu-san, who had started to nod sympathetically, froze mid-motion and stared at me with wide eyes. He looked unusually boyish in that moment—so much so that I wanted to keep staring—but I had already exceeded today’s eye-contact allowance, so I glanced away. Even an advanced-tier romantic like me has her limits.

Tilting his head slightly, as if questioning his own hearing, he asked,

"Sorry, could you say that again?"

"I succeeded in deploying two."

"…You succeeded?"

"I did."

"…………Wait, seriously?"

Right on cue.

I couldn’t help flashing a smug grin and throwing up a double peace sign.

Heh. What do you think, Ayumu-san? It’s not just Teio and President Rudolf. Sometimes I exceed your expectations too. So don’t you dare take your eyes off me, okay?

"No, but… what? Symboli Rudolf trained for years before she achieved simultaneous deployment. And you’re telling me you did it in a single day…?"

"This is the power of Hoshino Wilm!"

At that, Ayumu-san leaned back in his chair and stared up at the ceiling as if trying to process reality.

"I knew you were one of the greatest prodigies in history, but even so… I thought we’d glimpsed a realm unreachable within the Twinkle Series. If Symboli Rudolf hears about this, she might actually be depressed…"

As I chuckled at his groan, a voice came from the side.

"…Um, is this something I’m allowed to be hearing? Should I step out?"

It was Masa-san, who had been quietly working while very obviously listening in.

Honestly, I didn’t quite understand what she meant.

Ayumu-san, being her brother, seemed to understand immediately and gave a small shake of his head.

"No need. Masa is part of our camp too. There’s no problem with her knowing… at least, I don’t think so."

Ah. That kind of thing.

Masa-san tends to worry. Even after supporting us for so long, she still seems to feel like an outsider. It’s true that one day she’ll become a full-fledged trainer and lead her own team instead of working as an assistant. But for now, she’s giving her all for us. There’s nothing to hide.

Well—except the fact that I’m a reincarnated Uma Musume.

Since Ayumu-san was looking at me for confirmation, I added,

"It’s fine. This method probably only works for me anyway. There’s no real ‘technique’ to pass on."

Still wearing my smug expression, I said that—and Ayumu-san let out a quiet, understanding "Ah."

"I finally get it. You used enhanced cognition, didn’t you?"

"Ohh, impressive! Correct!"

A Domain can only be maintained for a brief instant at minimum, or just over ten seconds at most.

The reason is simple: the limits of our brains.

A Domain is the ultimate secret of racing Uma Musume. It’s similar to what human athletes call “the zone”—a state you can only enter by pushing your focus to its absolute limit and pouring everything into the race.

And that level of focus consumes an absurd amount of mental energy. During a race, our brains are flooded with performance-enhancing chemicals, so we don’t collapse immediately after closing a Domain…

Even so, there’s a world of difference in exhaustion between an all-out race where you deploy a Domain and a more controlled race where you hold it in reserve.

And that’s precisely why using two at once is so difficult.

Even one leaves you nearly groggy. Try to deploy two simultaneously, and your brain might as well explode.

That’s why simultaneous Domain usage is considered nearly impossible for an Uma Musume. A divine technique—one that even the strongest in history, Symboli Rudolf, required nearly ten years to master.

…However, even such a divine technique falls within reproducible range for a reincarnated, cheat-level Uma Musume like me.

"I have enhanced cognition during my ‘Ten-Sei Spurt’—not anime, I mean Ten-Sei. If the reason two Domains can’t be deployed at once is the brain’s processing limit, then I figured that in an enhanced cognition state, maybe I could handle it."

If the limitation comes down to brain resources—insufficient processing capacity—then wouldn’t someone whose cognition skyrockets be able to shoulder more?

In hindsight, it’s obvious. A real Columbus’s egg situation. The difficult part is thinking of it in the first place. After witnessing Rudolf-senpai’s simultaneous deployment and hearing Ayumu-san explain the theory, the answer finally clicked.

"I see. So instead of reducing the strain on the brain, you increase the brain’s capacity itself. Interesting. Unique. Truly something only Hoshino Wilm could pull off…"

Ayumu-san rested his elbows on the desk, laced his fingers together, and closed his eyes in thought.

Maybe it’s because he devoted his life to becoming a trainer, but when it comes to Uma Musume, he has a researcher’s temperament. He gets completely absorbed in analysis.

Not that I’m far behind. I enjoy experimenting too. Yesterday, Bourbon-chan and Souri-chan helped me run various comparison tests.

…We ran 3000 meters multiple times, so they were understandably exhausted.

Well, Bourbon-chan wanted to build stamina for the Kikuka Sho’s long distance, and we didn’t overdo it. So it’s fine. Totally fine.

"…Wait. In that case, could you further… how should I put it… increase the precision of a single Domain?"

At his sudden question, I shook my head.

"I tried that too. It didn’t work."

"It didn’t, huh…"

"At best, I can slightly extend the duration. It seems more like a matter of the Domain’s intrinsic precision… hmm."

Since this is largely a sensory phenomenon, I struggled to explain it to someone who can’t experience Domains firsthand.

Then I remembered an analogy Ayumu-san once used.

"If you compare a Domain to a painting, then increased cognition—expanded brain resources—is like making the canvas bigger. Just because the canvas gets bigger doesn’t mean you suddenly become better at painting, right? It’s the same thing. It doesn’t improve the Domain’s precision itself."

"Ahh, that makes sense. So you can paint more pictures—in other words, use multiple Domains—but you can’t enhance the inherent performance of each one."

"There’s a little extra room, so I can extend it by less than a second. But that’s about it."

That single second could be enough to overturn the tide of a race.

But that’s not the focus right now. Besides, if I’m deploying multiple Domains at once, that option is off the table anyway.

Ayumu-san took a sip of coffee and steered the conversation back.

"Sorry, we got sidetracked. So—you said you managed to use two Domains at once…"

"Yes. I’ve definitely reached the point where I can deploy them. That much is certain."

"…Judging by your tone, I’m guessing there’s a problem?"

That’s right.

I let out a quiet sigh and recalled yesterday’s results.

"There are about three problems. A small one, a medium one, and a big one. Which would you like to hear first?"

"It’s only natural that a newly developed technique would have flaws. I’ll help you sort them out. Let’s start with the smallest."

Strictly speaking, the smallest issue is already more or less resolved… but for the sake of thoroughness, I explained it anyway.

"First—the smallest issue concerns resource consumption. Simply put, trying to use two Domains at once dramatically increases the concentration they require."

"Ah… like multitasking. It’s easy enough to use both hands for the same action, but the moment you try to have your right and left hands perform different tasks, it suddenly demands much more focus and practice."

"That’s probably a good comparison."

I’ve never actually tried doing two completely different things with each hand, so I can’t say from experience—but it certainly sounds difficult.

…Though if I used Ten-Sei Spurt, I might actually be able to pull it off. Maybe I should test that sometime.

"Intuitively speaking, if a normal Uma Musume has ten units of brain resources, then deploying one Domain probably consumes eight or nine."

"And using two?"

"About fifty per Domain. So a hundred total."

"That escalation is absurd."

But that’s genuinely how it felt.

As a reincarnated, cheat-level Uma Musume, even when I’m not fully activating Ten-Sei Spurt, my cognition seems to be partially enhanced while I’m running. I can hear surrounding sounds more clearly too, which is probably thanks to improved neural processing speed.

Even so, when I tried deploying two Domains simultaneously without activating Ten-Sei Spurt, my head started to feel like it was boiling. Instinctively, I shut it down.

Honestly, the fact that Symboli Rudolf can maintain simultaneous Domains without any cheat-like abilities makes her nothing short of a monster.

"So… you’re saying Symboli Rudolf is performing something that would normally require 100 units of resources while keeping it down to 10?"

Masa-san’s voice carried a faint chill as she tried to confirm that, and I was just about to nod—

—but before I could, Ayumu-san shook his head.

"No. I don’t think that’s it. From what I observed, Symboli Rudolf lowered the output of one Domain—reduced its effect—to the level of a skill. Something she could use more routinely. It would still consume brain resources, of course, but I doubt it triggered the exponential cost increase Wilm described.

So most likely, instead of 8 and 9, she adjusted them to something like 2 and 8—or 3 and 7."

He said that so casually, but—excuse me, what?

"Um… lowering a Domain to the level of a skill? That sounds like a completely different kind of monster. Is that even possible?"

"It appears to be. That’s how it looked to me."

"Then… I suppose it must be true. As hard as that is to believe…"

No one understands better than I do how sharp Ayumu-san’s observational skills are—or how careful he is before drawing conclusions. If he states something this firmly, it’s practically confirmed.

Though he was also muttering things like, "Evolving inherited uniques into upper-tier skills… no, but that would require… unless it’s her personal unique… but then inheritance of will wouldn’t…" so clearly, even he hasn’t fully pieced it together.

…Sometimes I think Ayumu-san forgets that I have horse ears. His muttering carries surprisingly well.

When that happens, I get to hear how his mind works. It feels like a little bonus. And sometimes, he mutters compliments about my abilities—or even my appearance.

When that happens, I get so flustered I have to physically leave the room.

Even a so-called advanced-level romantic can’t handle unexpected praise.

"…From my perspective, both my brother—who can analyze that much from a single glance—and Hoshino Wilm, who can perform something that costs 100 units of resources, are unbelievable monsters."

Masa-san looked genuinely overwhelmed.

Well… Ayumu-san aside, I am a reincarnated Uma Musume.

Anyway—back to the topic.

"So yes, using two Domains dramatically increases exhaustion. But that issue is already resolved. My enhanced cognition can compensate for the increased load."

"I see." Ayumu-san nodded.

His eyes were on me, but his focus was distant. He was probably calculating how two Domains would affect a race—how much my performance would improve.

But that’s counting our victories too early.

We still had two more problems.

"That said… this overlaps with the medium-level issue. The exhaustion is so severe that my enhanced cognition drops to roughly normal levels.

If we consider safety, it might be difficult to combine this with Ten-Sei Spurt."

At that, Ayumu-san’s brows knit together.

"Hm… Ten-Sei Spurt in the final stretch is one of your greatest strengths. Losing that would be significant."

The Ten-Sei Spurt I developed during last year’s Takarazuka Kinen. By using Ten-Sei Spurt to redirect surplus cognition into my running, I achieve an optimized, maximum-efficiency form while minimizing stamina loss.

It’s saved me countless times. There are races I simply could not have won without it.

It’s essentially my second finishing move—on par with a Domain.

Giving that up, even in exchange for an additional Domain, would naturally raise concerns.

…Though, to be honest, the biggest issue still remained.

"Now then. The final problem. The biggest—and most fatal—one."

"…I don’t like the sound of that."

Sorry, Ayumu-san. But I think it’s worse than you’re imagining.

Even I was pretty depressed when I realized it yesterday.

"I did manage simultaneous Domain deployment. I truly opened two Domains at once.

…But that’s all I did."

"That’s all?"

I nodded and delivered the crushing truth.

"The Domain effects didn’t activate."

The atmosphere in the trainer’s office shifted instantly.

Confusion. Bewilderment. Suspicion.

An unpleasant tension settled over the room.

And then—almost immediately, in less than a second—Ayumu-san processed everything and asked quietly,

"…So, in other words—

You opened the Domains, but there was no acceleration or other effect. Your running didn’t change at all?"

"Yes."

Ayumu-san lowered his gaze slightly, his expression tightening.

It didn’t feel like blame. More like genuine confusion.

"No effect… why? You’re certain you opened the Domains, correct? And yet their effects didn’t manifest… a Domain malfunction.

Did deploying two simultaneously cause interference? Or was there a flaw in the method?

…No, this is pointless. There’s no precedent for deploying two Domains at once—not even in Horino’s past records. That makes it difficult to gather data, and even harder to isolate the cause."

Murmuring to himself as he organized his thoughts, Ayumu-san suddenly looked up at me.

"Wilm, I want your impressions. Did it feel different from when you open just one Domain?"

If it felt different? The answer was obvious.

"It did. …It’s hard to describe, but the scenery of the Domains kind of… got jumbled together."

"Jumbled? You mean the mental landscapes blended?"

"Something like that…? Honestly, I couldn’t make sense of it myself."

Domains are sensory experiences.

The scenery you see when you open one isn’t real—it’s more like an illusion projected by the soul of an Uma Musume.

And while I was an otaku in my previous life and can usually explain things reasonably well, I’m not naturally eloquent. Explaining this phenomenon is surprisingly difficult. I’d thought through the issues since last night, so I could manage the prepared parts—but improvising like this? That’s tough.

"It’s like… the sky and the flames and everything got tangled together.

If I compare it to a painting… it’s like cramming too many motifs into one canvas, and nothing feels cohesive."

"I see… That helps. I think I understand."

Covering his mouth with one hand, Ayumu-san began to reason it out.

"If I had to guess, deploying two Domains simultaneously your way is like painting two separate works on the same canvas at once.

Using your right and left hands to paint two masterpieces simultaneously would be impressive—but the result would be a chaotic painting, with both images overlapping and interfering.

Viewed as a single piece, it likely wouldn’t qualify as high quality."

"I see… So that’s why Symboli Rudolf reduced one Domain to the level of a skill?"

"No—even Symboli Rudolf probably couldn’t fully overlap two Domains the way you attempted.

I think what she achieved was a second-best solution to dual deployment—and it happened to mesh cleanly."

"Of course, that’s just a hypothesis," he added.

Well, at this stage, anything about Symboli Rudolf is speculation anyway.

But the “two paintings on one canvas” analogy felt painfully accurate.

"Then… simultaneous Domain use might just be impossible for me right now.

My Domain precision isn’t high enough to condense one into a skill, and if I try to deploy both at full power, they simply blend together.

And if I can’t even layer Ten-Sei Spurt on top of that, then it’s all risk with zero reward."

When I first managed to open two Domains yesterday, I was so excited I felt like my brain was drowning in dopamine.

But the reality? My cognitive resources were devoured, both Domain effects vanished, and running inside that warped, merged landscape felt incredibly wrong—almost nauseating.

Honestly, I was deeply disappointed.

Still, the data itself was valuable. And maybe—just maybe—Ayumu-san would think of something.

But as things stood, it felt hopeless.

Like he said, new techniques are born from failure. At the very least, I had succeeded in opening both Domains. That alone might prove useful someday.

…At least, I was beginning to resign myself to that conclusion when—

"Hm? No, there should be a way."

Ayumu-san said it as if it were obvious.

I blinked.

Given how the discussion had gone, hadn’t this seemed unsalvageable?

"It’s simple. Your failure occurred because you only had one canvas. But you clearly demonstrated the ability to paint two separate works at once.

If you had two canvases, simultaneous deployment should function properly. Wouldn’t it?"

He said it so matter-of-factly that Masa-san shot him a skeptical look.

"…You do realize the painting and canvas thing is just an analogy, right? Is that even possible? …What do you think, Hoshino Wilm?"

"Eh? Umm… I’ve never tried, so I can’t say for sure…"

Two canvases.

In other words, separating the worlds where the Domains manifest. That must be what he means.

But how?

If I activate Ten-Sei Spurt, could I split my thoughts in two? No… I’m not even sure how to conceptualize that.

As I groaned in thought, Ayumu-san continued.

"Wilm, you once said that the scenery of a Domain appears layered transparently over reality, like an overlay. Correct?"

"Ah, yes. That’s about right. Though it’s hard to explain."

"Then let’s treat that layer as the canvas. What if you add another layer—another canvas? What happens?"

The Domain’s scenery.

Treat that as a canvas—and prepare two layers…

Ah.

That was much easier to picture.

"…I might be able to do it. I’m not completely confident yet, but I can at least imagine how it might work."

When I nodded hesitantly, Ayumu-san smiled gently.

"Good. Then we’ve taken the first step toward true simultaneous Domain use.

From now on, alongside your foundational training, we’ll also experiment with refining this technique.

Your overseas expedition is approaching. We’ll need to work on this while adjusting to foreign conditions… Can you handle it?"

"! Yes! As long as I’m with you, Ayumu-san!"

A-alright. I’ll do it.

If Ayumu-san is placing his expectations on me, there’s no way I won’t rise to meet them.

Acclimating to foreign soil. Continuing foundational training for the Prix de l’Arc de Triomphe. And experimenting with simultaneous Domain deployment…

…Wait.

Isn’t that just blatant overtraining?

Wilm grew suspicious.