“The spine node circulates and balances the Kairo flow.”

“Ohh…” Hisagi nodded slowly, understanding dawning at last.

“So these three - solar plexus, spine, and heart node… they’re your lifelines,” Ren said. “If you’ve got high energy reserves, you automatically have high Kairo Energy.”

“Hmm… but Master,” Hisagi asked, frowning, “Sakura raised her hand for Avatar ability users. Why didn’t everyone? They can get the Favor, right? Even Kazuma-master didn’t raise his hand at first.”

“Oh, that?” Ren scratched his head. “He didn’t just raise it because he didn’t want to. But that’s exactly what I’m going to explain.” He shifted closer. “There are three core types.”

“Core types?” Hisagi blinked. “Wait—” He started counting on his fingers. “Then total… twenty?”

Ren smacked the back of his head lightly. “Did I say nodes? I said core types. Listen properly.”

“A-Ah, hehe~.” Hisagi rubbed his head awkwardly.

“First type: Mono Core. It’s the most common. Only one core, and you can awaken just one kind of power type. That core is in the Solar Plexus.”

“What’s your core, Master?” Hisagi tilted his head, eyes curious.

Ren sighed, eyes rolling. “You won’t listen to other cores either, huh? …Mono Core.”

“Okay, okay,” Hisagi said quickly. “Then what’s the second?”

“Dual Core,” Ren said. “It’s rare. I don’t know everything, but from what I learned… both parents have to be from a bloodline. Even if they themselves don’t have the core.”

“Even if they don’t have it?” Hisagi’s brow creased in confusion.

Ren threw his hands up. “Hey, you baka, wait… I’ll explain with an example.” He pointed at himself. “I’m Mono Core, right? But Sakura’s Dual Core.”

“Eh?”

“My mother came from a Dual Core bloodline. Even though I’m not a user, I came from that line.” Ren’s voice softened. “I don’t know about my father… my mom never told me.”

Hisagi looked up, mouth twisted in thought. “What is Dual Core bloodline? Wait! Then Kazuma-master’s parents are from the same line?”

“Um…” Ren replied. “Long ago, some people experimented… tried creating a second core. They thought more power meant better.”

His gaze dropped. “But due to its effects, most of them died. Only a few survived, and the trait got passed. Maybe Kazuma’s parents were from one of those. Who knows.”

“Hm…” Hisagi tapped his chin. “So, Dual Core users get Avatar Ability, right?”

“Master, then wait!” He said, back straightened. “Um… who raised their hands?...”

“Kazuma-master, Sakura, Yuta-san… a boy named Ish… uh, I forgot his name.” His brow furrowed. “Then why didn’t Yui-san raise her hand? She’s Yuta-san’s sister, right?”

“Oh? You remembered that much?” Ren raised a brow, then gave a small nod. “Well… like I said, I only know a bit. Um… it depends on the situation at birth too.”

“Then Sakura’s lucky she got it?” Hisagi asked, leaning forward slightly.

Ren’s eyes narrowed. “Did I say she is lucky?” He flicked Hisagi’s forehead again. “I told you, right? Most people who got it died from it. If they don’t use it properly, they’ll… die.”

Hisagi’s eyes widened. “H-huh? You mean Sa—”

Smack. Ren hit the back of his head again. “Don’t say that kind of nonsense.”

Hisagi rubbed his head sheepishly.

“Listen,” Ren continued, his voice firm now. “The second core, in their case, appears in the spine.” He drew a short breath. “But they can’t activate the spine node.”

“Without it, anyone can only use six nodes. With spine… they can go up to nine. Or even ten, if they train hard.”

“Then… Master and Sakura?”

“Yeah. They can’t. But in return, those core users get a second type of ability. It’s not like the main core in the solar plexus. It’s small, but still useful.”

“Then what does Master have as his second type? I know he can use lightning.” Hisagi leaned forward eagerly.

“Oi. What’s this weird obsession with him? ‘What did he have? What did he get?’ Huh? Repeatedly?” Ren scowled. “I don’t know! He said he hasn’t awakened anything yet.”

Hisagi shrank back a little, laughing nervously.

“Well,” Ren exhaled, folding his arms. “Listen properly now. The third type… is very rare. Those people can use all fourteen nodes, of course, with the three main ones too.”

“W-what?” Hisagi’s mouth fell open. “All nodes? That’s real?!”

“Yeah,” Ren said calmly. “Hm… All three core type users can use the solar plexus, spine, and heart. But Dual Core users can’t activate the spine, it only balances the flow.”

“So, what is the third type?!” Hisagi asked, eyes narrowing with curiosity.

“You don’t need to know that right now,” Ren said. “Didn’t I say earlier about ‘level 200?’ After 200… if they can’t go beyond that level, then they’re the third type.”

“After 200, it all depends on you. No matter the level.” He gave a tired grin. “You can mostly do what I do, but just in a limited way.”

“The third one sounds super strong.” Hisagi’s eyes lit up. “No wonder it’s rare!”

Ren didn’t reply, just watched him with an unreadable look.

“Okay, next.” Hisagi leaned forward, fingers tapping his lap. “Wait! Do you activate the spine node, Master? You’re Mono Core, right?”

“Yeah, I have it,” Ren said simply, then he shook his head. “And for today… that’s enough. Your brain won’t survive if I say one more thing.”

“Eh? Master, please,” Hisagi begged, leaning in dramatically. “You didn’t even explain what Controller or Sensemitter or other types mean and how do you activate the spine node?!”

Ren sighed, rubbing his forehead. “That’s why I didn’t say. You won’t get it now.” He gave him a flat look. “And how would I know about Sensemitters, huh? I’m not one.”

“But please, Master… just a little.” Hisagi pressed him.

“No.”

“Th-then at least tell me how to increase Kairo energy. That’s important, right?”

“Inori said it clearly, right?” He exhaled through his nose. “From the next rounds onward—”

“I know, Master!” Hisagi nodded fast. “I was there too when Inori-sama said ‘no Kairo combat, only brain.’ But I’m serious now!”

“Uff…” Ren dropped back against the wall. “Kazuma gave you a book of herb information, right? Remember?”

“Haa, of course I remember!” Hisagi grinned. “Because of that I increased my Kairo energy and passed the first test, right?”

“Well now it’s gone,” Ren said flatly. “It was only temporary. Just enough for back then.”

“Huh?! Then now I don’t even have 100?” Hisagi’s eyes widened.

“No,” Ren said. “It increases only through proper ways - meditation, training, and pushing limits while fighting…” He gestured toward Hisagi’s belly. “That’s how the reserves in the solar plexus grow. When that increases, it starts generating more Kairo.”

“Ohh…” Hisagi looked down, thinking. “Then really I don’t have it?”

Ren slapped his own forehead. “Didn’t he just say it was temporary?”

“So… I can’t use mind voice exchange art?” Hisagi’s tone deflated. “I thought I could do it with you now.”

“You wanna do the agreement… with me?” Ren gave him a long stare.

“I-I mean, M-master! Don’t you wanna do it with me?” Hisagi stammered, cheeks flushing.

“Stop making that face.” Ren sighed. “Alright, can I take the scroll or will you use that? Doesn’t matter. Scrolls for that art are common, not rare.”

“Huh?” Hisagi blinked. “But I don’t have enough Kairo energy, right?”

“So what?” Ren waved him off. “You still believe what that idiot said? He only said that to make you curious and raise your Kairo. You didn’t even cross 100. Did you at least use them properly?”

“I did use them, Master!” Hisagi pouted. “I’m lucky this year they decreased the requirements.” He stood up quickly and grabbed the scroll from the shelf. “So… can I?”

“You’ve got enough Kairo. Don’t worry.”

Hisagi unrolled it carefully. Two circles were etched in the middle.

“Kazuma-master told me I have to send a link… how?”

Ren walked over and tapped lightly near his belly. “Here. Solar plexus. Now think. Imagine a line moving from there to your brain, and then to this scroll. It already flows like that, but unless you imagine it, you can’t use it for your own will.”

Kazuma opened the door and blinked at the scroll laid neatly on the bed. “Huh! Oh, you’re using it now?” He looked toward Ren. “You agreed?”

“If I don’t,” Ren muttered, “will he even listen?”

Kazuma chuckled and turned to Hisagi. “Oi, did he say any basics or just hit you again?”

“He explained some things! But he stopped in the middle—”

“That’s enough for you.” Ren crossed his arms. “For now, you just need to keep increasing your energy in free time. Later you can train with the katana.”

“Then why’d you scold me, huh?” Kazuma raised a brow. “You didn’t tell him fully either.”

“You idiot,” Ren glared. “Sakura can already use them. You should’ve explained her clearly. I told him, even though I don’t know his core type yet.”

“That’s because he probably asked you,” Kazuma shot back. “He saw the others raise their hands.”

“Master, how do we even know what my type is?”

Kazuma gave Ren a side glance. “See? He’s asking doubts about core types. Means he definitely asked. So you did tell him.”

Ren sighed, clearly losing the battle. “You’ll never admit you’re wrong, will you, idiot?” He turned to Hisagi. “I already explained the third type, right?”

His tone sharpened. “It can be known after you cross level 200. That’s the only way we’ll know your true type. But we can test if you’re Dual Core or not.”

Kazuma tilted his head. “You think he’s the third type?” He smirked. “I’ll be very happy if he is not.”

“You’re jealous, Master.” Hisagi grinned wide, teasing. “I’ll have a strong core and beat you!”

Kazuma narrowed his eyes. “Huh? Who said that?” He turned to Ren with suspicion.

“Hey, I didn’t say that fully!” Ren raised both palms. “I stopped midway because he wouldn’t understand if I overloaded him with info!”

Kazuma shook his head with a laugh. “And you’re the one who told me I should’ve explained more.”

“Master!” Hisagi leaned over, excited. “First see the scroll!”

“Wait.” Ren stopped him with a hand. “Let’s test your core type first. Then you get practice with the Kairo energy flow too.”

He held out his hand. “Kazuma, give me it.”

Kazuma pulled out a thin, square piece of pale sand-brown paper from his coat. The edges were sharp and even, the texture dry and slightly stiff. “Here.”

Ren placed it carefully on the floor. “Alright, now send your energy into it. This is how you practice.”

“Eh? What is this paper?” Hisagi tilted his head.

“That’s Nihona paper,” Kazuma said, folding his arms. “If you have a Dual Core, it’ll show the result. First, put your finger on it.”

“Okay…” Hisagi carefully placed his finger on the paper. Nothing happened.

“Master,” he whispered nervously. “It’s not doing anything.”

“Did you just place your finger, or did you actually transfer energy?” Ren raised a brow.

Before Hisagi could answer, Kazuma smacked him lightly on the back. “Nope. Nothing wrong with hitting you.”

He pulled out another sheet. “Here. Watch properly.” Kazuma laid it flat on the floor and tapped the center with his index finger. A faint green aura shimmered beneath his touch. Tsshh! A small pop crackled out.

Two circles etched themselves near the center of the paper; one big, one small, side by side. He lifted the sheet. The circles had burned clean through, leaving two neat holes.

“See?” Kazuma turned it for Hisagi to look at. “That’s the result you get if you’re a Dual Core. The center gets sliced, and the energy bursts out.” He gestured at the sheet. “Try again. If it doesn’t happen, then you’re not Dual Core.”

Hisagi placed his finger again, eyes squeezed shut. ‘Imagine… imagine a line flowing to my finger…’ he thought to himself.

A tiny white aura flickered, faint and shaky… then vanished. Nothing happened.

“Um…” he peeked open one eye. “Then I’m not Dual Core, right?” Quietly, he handed the paper back to Kazuma.

Ren glanced at it. “Then you’re probably one of the other two types.”

“Okay, no problem!” Hisagi turned eagerly toward the scroll. “Master, let’s drop our blood now and transfer! I get it now!”

Ren reached for his katana.

“Wha—Master?!” Hisagi leaned back nervously.

“I’m just going to cut a little. Don’t panic.”

“W-We can use a kunai too, right?”

Ren chuckled and picked up the kunai instead. He pricked his finger and let a drop fall into one of the scroll’s circles and wrote his name beneath.

Hisagi did the same, a bit nervous, but didn’t flinch.

“Now, transfer it,” Ren said.

“Into my circle, right?”

“Idiot, no.” Ren narrowed his eyes. “You’re supposed to transfer into my circle. I’ll transfer into yours.”

“Oh.” Hisagi nodded sheepishly. “Got it.”

Both closed their eyes, imagining a line flowing from their solar plexus to their brain and then outward into the circle.

A fine line etched itself between the two blood-marked circles.

“Hmm… you did it.” Kazuma, standing nearby, folded his arms. “Try it now. Talk to him.”

Hisagi shut his eyes, concentrating. ‘Master.’

Ren didn’t react. “Say something already, idiot.”

“I did!” Hisagi opened one eye. “Didn’t hear me?”

“Nope,” Ren muttered, then focused. A moment later, his voice echoed in Hisagi’s mind, – Are you listening now?

Hisagi gasped. – Yes! Master, I’m hearing you!

“Good. Now try again. I heard you just now. But unless you can create the link yourself, you won’t be able to talk anytime you want. Try again like you did before.”

Hisagi tried again, eyes shut tight, brows creased. Nothing.

“Oi, you talked when he connected, right? Then what’s the problem now, idiot?” Kazuma raised an eyebrow. “You need to know more. Even Sakura does better than you.”

“Huh?” Hisagi scowled at him. “She’s been trained for four years, Master! I just started. You didn’t even teach me anything in between… did you ever ask me if I wanted to learn?”

Kazuma chuckled, rubbing the back of his neck. “Okay, okay. That one’s on me. Sorry. Is it okay now?”

Hisagi squinted at him, suspicious. “You really just said that?”

“Whatever,” Kazuma grinned, waving it off. “Take full rest. You’ll need that brain tomorrow.”

Hisagi groaned and flopped onto his bed. “Well, at least I learned a little today… Master, when can I learn more techniques?”

“First just increase your energy. Then I’ll tell you.”

****

– ‘Hey, Yui, give me control,’ Yuki whispered from within. ‘And don’t take it back. Just sleep, okay?’

– “What do you want to do?”

Her tone softened. – ‘I didn’t know Maa fully before… At least now I know something. I just want to…’

– “If you didn’t sleep when you arrived in this world,” Yui said gently, “you would’ve talked more with her.”

– ‘Dummy,’ Yuki muttered. ‘Don’t argue. Just give me and don’t forget what I said, okay?’

Sakura lay on her bed, flipping through a book. Airi sat beside her with a bag of chips, munching.

“Hey,” Airi asked again, “you really don’t want these?”

Sakura shook her head slightly. “No need, Airi-san.”

Just then, Miko opened the door.

Yuki rushed forward and hugged her tight, so suddenly that Miko stumbled slightly, completely thrown off.

Sakura and Airi turned to glance but didn’t speak, letting the moment breathe.

– “Hey! What are you doing?” Yui’s voice rang faintly from within.

– ‘Just sleep, you idiot,’ Yuki muttered under her breath. ‘Don’t disturb.’

“Yuki?” Miko blinked, arms still awkward around the girl.