They arrive at the border camp before noon. It's both what she expected and yet not.
The tents are big and green, and Konoha's leaf symbol is on basically everything. The red Uzushio swirls are a familiar pop of color on everyone's back. She recognizes a couple of other clan symbols—namely a group of Uchiha eating at a rough-hewn table, laughing at each other's jokes.
And it's all kind of… out in the open? Shouldn't they be concerned about being seen?
Sensei sees her judging and gestures to one of several tall wooden posts. There are large paper seals plastered on them.
"Hidden? Can seals cast genjutsu?"
Minato hears the word 'seals' and jumps on it from there.
"It's so much more than genjutsu, Honōka-chan! Do you see the smaller character there? That one means—"
"Mirror. Yeah, I know. I can read, you know?"
He's unfazed by her retort.
"These seals are from Uzushiogakure originally, and they create a complex barrier that affects the way this area appears from afar. It mirrors the surrounding environment to hide the camp and has a secondary feature that confuses those who approach the camp into gradually getting turned around."
"How come we weren't affected?" she asks.
"Orochimaru-sama has the counter seal." Kakashi says.
She turns around and starts walking. "Sensei, stay. I want to see what it looks like."
His lip twitches. "Do not get lost."
"Kakashi, why don't you go with Honōka-chan?" Minato suggests. "Stay out of trouble, yeah?"
Kakashi sighs and catches up to her with a shunshin.
"We're supposed to be meeting with the captain of the border patrol, not playing in the woods, Honōka."
"We're not playing in the woods, we're inspecting the barrier, Kakashi-senpai."
He rolls his eyes at her weak attempt to appeal to his ego. It only worked the first few dozen times. He learned his lesson after she tricked him into a three way weed plucking competition with Guy while she reaped the reward for the D-rank herself. She bought them lunch afterward with the money though, as was fair.
They stop and look back.
"Are we outside the barrier yet?" she asks.
"You tell me. You're the one with the sensor ability."
"I couldn't even tell there was a barrier in the first place?"
"…It's probably farther out."
They walk another fifty meters or so, and Kakashi suddenly pokes her in the side.
"We're outside." He says. "What's it look like to you?"
She stares back at the camp; squints.
"Minato-san lied. It has to be genjutsu."
"He said it was 'more' than genjutsu," Kakashi says. "Are you sure you can't sense it somehow?"
"Give me a second. I'll see if it's a frequency thing."
"Do I even want to know?"
She sticks her tongue out at him and concentrates.
The more she uses her sensor ability, the harder it becomes to define. Even before, as Tachibana Tomoe, she had something that wasn't quite normal. And then she became Tsunemori Honōka and Might Duy asked her if she could mold chakra. Suddenly, there was a whole scientific phenomenon to explain what she felt and why.
What she feels is the real and very tangible energy contained within the chakra that makes up a person's chakra signature. Why she feels it depends on two variables; her emotional hypervigilance, empathy; and her heightened chakra sensitivity, her sensor ability.
The problem is, there are so many facets to any given chakra signature; rotation, ratio, quality, quantity, nature affinity… And her empathy blurs the line between what is physically present and what is not; emotions, psyche—the more spiritual aspects.
She facepalms. "Kakashi, I'm an idiot!"
He shoots her a wary look at her outburst. "Did you have another epiphany? Should I get Minato-sensei or Orochimaru-sama?"
"No, well, maybe…? Kakashi, I've been using my sensor ability ALL wrong!"
"…Okay?"
She wants to shake him, or maybe herself. He takes an exaggerated step away from her.
"Remember when Jūn-sensei talked about yin and yang chakra?"
"Sure. Which part specifically?"
"The Tale of Heaven and Earth part."
"Okay, yeah. I remember."
"Sensors sense chakra!"
"…yeah, Honōka, I kind of thought that part was obvious."
"Sensors sense physical chakra. But there's also spiritual chakra. I sense emotions—no one else does. Therefore, my sensor ability must sense both physical and spiritual chakra!"
"So," he's getting impatient now, "can you, like, sense the barrier now?"
"What? No? It's clearly genjutsu, or something."
"Honōka, genjutsu is yin-based chakra. Spiritual chakra. You just argued that your sensor ability is probably yin-based. I'm seeing a problem here."
She squints at him and back at the barrier that she's just not seeing.
"That is a problem, isn't it?"
They converge on their teachers when they finally finish speaking with the border patrol captain and his vice-captain.
"Minato-sensei—can fūinjutsu be genjutsu too?" Kakashi asks. "Honōka can't see the barrier or sense it."
"Eh? She can't?"
"Not at all," she groans. "Normally I wouldn't care, because genjutsu doesn't even affect me, but if I can't even sense genjutsu being used, that's a major problem." Especially if genjutsu is being used on the people close to her.
"That is a major problem." Sensei agrees. "You do not sense the barrier at all?"
She shakes her head.
Sensei forms one handed seals and Kakashi momentarily goes doe eyed, before quickly breaking himself out of it. He shoots Sensei a glare.
"And that?" he asks.
She bites her lip and shakes her head. "Nothing."
Sensei walks away, and they follow. They sit on folding stools at a fire pit that is embers only.
"Honōka thinks her sensor ability is yin-based—"
"Yin-yang, actually, because I sense—"
"Physical and spiritual chakra." Sensei finishes. "That would be the logical conclusion."
She opens and closes her mouth. Sensei weaves his fingers together in front of his mouth and smirks.
"Sensor types have a nearly uniform way of describing what they sense, Honōka-kun. It mostly involves picking up on waves or vibrations from chakra signatures. Frequencies, as you have described it. There are also sensors who would call individual chakra signatures 'big', or 'small', 'warm', 'staticky', and so on.
"However, being able to sense a chakra signature does not allow a sensor to understand intimately the emotional state of their target. What you do is highly unusual, therefore it differs from the standard sensor type. The conclusion I came to, given your predicted chakra ratio, is that your sensor ability is a pure Yin-Yang Release."
She pauses. She's never heard of Yin-Yang Release—or Yin Release, or Yang Release. The Academy only taught her that there are five elemental releases, several advanced elemental releases, and that certain jutsu require either more physical chakra, or more spiritual chakra. There's also the way he described her ratio just now.
"'Predicted' ratio, Sensei?"
"Ah, yes. Your class used the Uzumaki chakra aspect papers. A convenient bit of seal work, that."
She's sensing a 'but' in there somewhere.
"Chakra ratios are a relatively new theory," Minato explains. "Or, they are in the Land of Fire. It was pretty commonly accepted in Uzushio, before it fell. Ways to determine how much physical chakra a person has have existed for a couple centuries already, but spiritual chakra has been—kind of?—a myth for most that time."
She frowns at him, and Kakashi backs her up with a disbelieving stare.
"Genjutsu is yin-based though, it uses spiritual chakra—they teach that at the Academy." Kakashi says.
"It's more like…" Minato scratches his head. "We have reason to believe it exists, even if we can't actually prove it?"
Kakashi groans. He doesn't like theoretical work. Honōka does, though.
"I think I get it. Guy has a lot of physical chakra, but very little spiritual chakra. If spiritual chakra can't be calculated by itself, then the Uzumaki seals we used determined the maximum amount of physical chakra he could use. Because there would be physical chakra left over, it supports the existence of spiritual chakra, which in theory is mixed with physical chakra to use ninjutsu. In Obito's case, he could use all of his physical chakra without succumbing to terminal chakra exhaustion, therefore, he has a greater amount of spiritual chakra. Other factors can then determine the ratio, like quantity and quality."
"Yeah, that's more or less how it works!" Minato says. "Are you sure you don't want to learn fūinjutsu? I think you'd be good at it, Honōka-chan."
She blows a raspberry at him. Kakashi pushes her off her stool.
"But why can't Honōka see or sense the barrier?" Kakashi asks. "She clearly has spiritual chakra and can probably use that Yin-Yang Release Orochimaru-sama mentioned."
"I initially assumed genjutsu would not affect Honōka-kun because of her balanced ratio, as it suggests that her Chakra Pathway System operates at maximum efficiency—any attempts to disrupt the network would simply fail." Sensei crosses his legs. He's frustrated about something, missing something. "This may still be true. The problem now is that Honōka-kun is incapable of detecting genjutsu the usual way."
"What's the usual way?" she asks.
"Getting caught in it and dispelling it." He replies, dryly.
"Why can't I sense it with Yin-Yang Release? I can sense what people are feeling—that's the influence of their spiritual chakra on their physical chakra, right?"
Kakashi crosses his arms at her. "You just said it yourself, dumbass—spiritual chakra can't be calculated—it's undetectable by itself. And when someone uses genjutsu, they separate their spiritual chakra from their physical chakra. So, if there's no physical chakra to channel the emotions from the spiritual chakra, it blocks your sensory perception."
"…"
"Kakashi, nicely said!" Minato exclaims, offering him a high-five. Kakashi blushes and awkwardly reciprocates, but she can tell he's pleased with the praise.
She pouts. Is Minato just going to ignore the fact that Kakashi called her a dumbass to her face?
"There's got to be a way for me to fix it though, right?"
"No technique is perfect, Honōka-kun." Sensei says. "It is enough that you are now aware of your technique's weakness."
She's not really satisfied with that—might never be satisfied with it. She'll have to figure out some kind of workaround.
"I guess."