Driven by Blood

Throughout the Shinobi World, plenty of ninja used blood to help perform jutsu, but very few jutsu required blood as a medium.

As part of the body, blood was an excellent conductor of chakra. The materials used to inscribe Sealing Jutsu, barriers, and formation runes generally contained at least some animal or even human blood. When Mizuki used Summoning Technique, the jellyfish were so unintelligent that he often used his own blood to strengthen their connection and make them easier to control.

Another typical example was jutsu that pushed the body past its limits. They placed an immense strain on the blood and other parts of the body, and secret techniques that burned one's life essence to fight to the death were common.

Aside from those methods, there were also sacrificial techniques. The most famous example was Hidan of the Akatsuki. His Jashin Ritual, which used his own or someone else's blood as an offering, was an extremely strange and evil curse technique.

Mizuki didn't know whether the principles behind Summoning Technique had anything in common with this kind of sacrifice. But look at the Aburame Clan's Insect Manipulation Technique: it was a secret technique that traded the user's chakra and used their body as a nest in exchange for insects that would fight for them.

So, generally speaking, unless the summoner was in a situation like Mizuki's, where he took the lead and the summoned creature was extremely weak, it was hard to believe a summoned creature would come help in battle without any cost at all.

What's more, high-level summoned creatures were intelligent beings. The most exceptional among them, such as the Toad Sage, the Snake Sage, and Katsuyu's true body, were among the most powerful creatures in the world. Without some motive, how could they possibly meddle in conflicts between humans? Even if Kaguya Otsutsuki were revived and enslaved all of humanity with Infinite Tsukuyomi, turning them all into White Zetsu, what would that have to do with them? Toads would still eat bugs, and giant snakes would still eat frogs. Why go to all that trouble to prophesy about a child of destiny?

If there was one famous technique that required the user to give something up, it was undoubtedly the Dead Demon Consuming Seal. The user gave up their soul to summon the mysterious Shinigami, which then attacked and sealed the target's soul.

Summoning Technique, as its name suggested, could be understood as a jutsu for communicating with certain beings. It wasn't the same kind of technique as the Dead Demon Consuming Seal, but the underlying principles did seem somewhat similar. The only thing Mizuki couldn't figure out was what summoned creatures actually got from humans. Or rather...

"Could they get no direct benefit from humans at all, but gain something indirectly from this world? If so, that's certainly possible, but without seeing the actual Summoning Contract, I can't say for sure."

With that thought, Mizuki picked up the materials on Summoning Technique again and read for a while, but found nothing.

"Looks like I'll have to investigate properly. I can't jump to conclusions."

The next morning, Mizuki checked on the Bootleg Jinchuriki, who was still recovering from his injuries. His condition had stabilized, and he was out of danger. He'd had no choice but to test a brute-force version of space-time teleportation to escape this time.

Before he'd created the Bootleg Jinchuriki, Summoning Technique had worked, but now it didn't. A careful examination quickly revealed why: summoning was a jutsu between two individuals, but the Summoning Contract now recognized him and the Bootleg Jinchuriki as the same person. Ordinary Summoning Technique no longer worked; at most, he could use certain methods to strengthen the sensory connection between the two. If not for that, Mizuki wouldn't have needed to hurry to develop Space-Time Ninjutsu. But he hadn't expected genuine Space-Time Ninjutsu to be so difficult—it had completely exceeded his expectations. That was why he'd become so interested in a jutsu like Summoning Technique, which could achieve space-time teleportation. Only now did Mizuki truly appreciate how powerful the Flying Raijin Jutsu was, a Space-Time Ninjutsu developed from reverse summoning.

Many injured examinees were receiving treatment at Konoha Hospital. Mizuki had no missions at the moment, so not many people came to bother him. As he passed the wards, he occasionally saw someone being carried out, their face covered and their body already dead. A few of them were people Mizuki himself had rescued.

When he arrived at the special care ward on the top floor, Kakashi was already waiting for him.

"What did you call me here for, Kakashi?" Mizuki asked as he entered. He glanced around and saw several Anbu standing guard.

"You've seen it yourself. Sasuke is badly injured," Kakashi said, gesturing toward him. "But he still has to take part in the third Chunin Ninja Exams in a month. I need to give Sasuke some special training, as well as protect him."

"So?" Mizuki asked, puzzled. "You didn't call me here just to show off your teacher-student bond, did you?"

"Let me finish," Kakashi said patiently. "Protecting and training Sasuke alone will take up a lot of time, but all three of my students made it to the third exam."

"Oh, I nearly forgot to congratulate you, the Konoha Technician. You're quite the teacher."

"Cough, let's leave that aside for now," Kakashi said awkwardly. Aside from some basics, he really hadn't taught the new Genin much. "So my other two students are temporarily without guidance. It's important to improve them in a targeted way before the third exam, so I asked Ebisu to help Naruto, who has the weakest fundamentals, catch up."

"Oh," Mizuki said, understanding. "You want me to train Sakura, then?"

"Yes. Please help."

"You've got it wrong," Mizuki refused. "Ebisu is a Special Jōnin who specializes in teaching. Asking him makes sense, but why ask me? You can't say you're not playing favorites."

"Don't reject me just yet," Kakashi explained. "During the last preliminary exam, Sakura figured out that it was a test from the village, so she asked who the examiner was."

"So you sold me out?"

"I wouldn't call it that," Kakashi said. "Sakura herself asked for you to teach her."

"Oh?" That was unexpected. "What good would I be? Her opponent is the strongest Sound Ninja, and the gap between them is enormous. Does she have something in mind?"

"I don't understand girls' thoughts, but I really couldn't find anyone else suitable to teach Sakura."

"So you're dragging me in to fill the gap?"

"Not exactly. With your abilities, you could teach her Sealing Jutsu, Barrier Ninjutsu, or genjutsu. Sakura can't learn anything too advanced in those areas yet, so there wouldn't be much difference between you and me teaching her. And there's nothing else that could quickly improve her strength for now."

"Sealing Jutsu and genjutsu might be useful, but what's the point of learning barriers? She'd be better off resting and conserving her strength. That opponent's sound-wave attacks are too much trouble."

"I'll leave it to you, anyway. Let Sakura study whatever she wants. Use your judgment."

"Since you've put it that way, fine. But..." It wouldn't hurt to do Kakashi a favor. Still, it'd be even better if he could return the favor right away.