After the whole affair with Erina and Amelia in the room, Kai headed out for the first time in a week. He quickly headed to the practice field and watched how everyone had progressed.

Yoko looked like she was able to use Flash Step three consecutive times. Iori and Date could do twice while the rest could only do once.

But it didn't matter how many consecutive times someone can do it, the most important was that it could be used.

"Kei, how's your progress on Reverberating Fist?"

Kei temporarily stopped his Flash Step training and went towards a straw doll. He closed his eyes for a few seconds, breathed in deeply then accompanied by a yell, he punched the straw doll.

"Ha!"

Right after Kei's fist landed, the straw exploded.

"Good, you've managed to learn the basics but you're too slow in attacking, it's useless in a fight."

After grumbling about how it was nearly impossible to do it in that short amount of time, Kei kept on training.

"Date, Forceless Block?"

Kai's fist headed towards Date. The latter quickly got into position, he used the back of his hand to block the fist but before the impact could hit him, he slid down Kai's fist towards his wrist then to his arm then he swept it to the side.

"Good but that only works for straight punches. Try it again but try to use your wrist better, make yourself feel that you have no bones on your wrist."

After giving him tips, Kai headed towards Yoko.

"How much did you progress on Gentle Fist?"

"...Not much."

"That's fine, you'll do better soon."

After ruffling Yoko's hair a bit, much to her confusion, he headed for Arata.

"Arata, Steel Body."

Before even giving him time to prepare, Kai's fist headed for Arata's chest. It had enough power to blow away Arata in his normal state but if he employed the technique that Kai had taught him, it wouldn't do much.

After seeing Kai approaching him, he used the technique Kai taught him. The muscles in his body strengthened and enlarged, the tissues became tougher, and his skin became as hard as a tree.

Unfortunately, it wasn't enough as he could still feel the pain and the technique was canceled.

"You're on the mastery of wood, you're far from reaching steel. Your tendons weren't strengthened, try again."

After hitting Arata one more time, he headed for Iori, he hadn't taught him any techniques other than Flash Step but Yoko still made more progress than him.

Naturally, he was punished.

He checked on each of their progress more than once and gave some tips. He gave them multiple situations to adapt to and made them practically use their skills.

It was already a great feat about how they managed to reach this level in a little more than week because most people would take months.

"Everyone, gather around."

After checking on them for the last time, he called them over. Before he did an explanation, he used a fighting stance with both of his hands curled into fists, one below eye level and one above eye level.

"You will all come at me one by one and I will show you the potential of your techniques. I can tell that you all aren't really convinced about any of them other than Flash Step so I'll personally demonstrate it. Don't underestimate physical techniques. I'll limit my strength output to C-class."

He pointed towards Kei. The latter immediately understood the meaning and charged forward, he used Reverberating Fist but just before it hit Kai, he dodged and without even the slightest preparation, he hit Kei square in the chest. After a small delay, Kei's body rumbled as if an electric shock passed through him.

A mouthful of blood was released from Kei's mouth as a lot of his organs were damaged and some were even pulverized on the spot. With just one hit, Kei was brought to near death.

"This is the power of Reverberating Fist."

Kai quickly began healing Kei and once he was healed up, he called Date.

Date's body was nearing A-class but Kai limited himself to C-class. Naturally, Date didn't hesitate at all to attack Kai with his full power. In his eyes, Kai was a monster after all.

But that was wrong, once Date's punch made contact with Kai's arms, the force gathered within them was suddenly expelled to the side where Kai redirected Date's arm.

Normally, that punch would've landed on Kai's chest but right after Kai moved Date's arm, the floor beside them cracked. Before Date could react, Kai used Reverberating Fist. Date met the same fate as Kei.

After healing Date, Arata was up next. Arata attacked first, using up all of his power but forget hurting Kai, Kai didn't even twitch. His feet were still in the same spot and Arata's hand felt like it had hit a giant steel wall.

"Ugh..."

Arata crouched down from the pain but Kai lifted him up to use another Reverberating Fist. It was unnecessary to use the technique on all of them but for some reason, he had a smile on his face everytime he did so.

"..."

Iori who was next on the list, grimaced. What kind of person would have a smile on his everytime he destroyed his friends' organs? Tracing this line of thought, he began to shudder.

"H-hey, Kenji. I think I want to train a bit more."

"And that's what we're doing right now. Come here."

Facing the silent pressure from Kai, Iori didn't know whether to laugh or cry. What kind of training involved having the inside of your body turned into mush?

Although Iori was sure before, his thought was definite now. Kai was a huge sadist. Not only was Iori hit by Reverberating Fist, Kai even hit him in several other places before finishing him off. The amount of pain he felt in those seconds couldn't be compared to anything he had ever felt before.

Now, he knew for certain why everyone called Kai a demon when it came to training. He didn't hesitate to critically injure those he trained because he had confidence in being able to heal them.

In fact, he had even forgotten that Kai did this to show them the potential of physical techniques and not just to give them fear.

Kai was using the power of C-class but without protecting inside their bodies, it was futile to even try and contest. Reverberating Fist sends all of the power, the force behind the attack into the opponent's body without harming the outside. The force spreads throughout the body and depending on the mastery, more force could be transferred inside.

Forceless Block was something derived from Gentle Fist, it took the opponent's force and redirects it to somewhere else making the attack lose all power behind it.

Steel Body was Body Enhancement without the use of mana. The principle behind it was strange because the body could be strengthened without the use of mana but the user wouldn't be able to move because of the tensed muscles.

Now, it was finally Yoko's turn. Seeing what happened to those who came before her, she gulped. She took her stance to prepare using Gentle Fist and Flash Step.

The moment she vanished, Kai held out his palm sideways and sure enough, Yoko's fist was caught. He clenched his free hand and aimed for Yoko's side.

As if she was expecting that, Yoko avoided the fist by a hair's breadth and used a palm on Kai's chest. Unfortunately for her, Kai quickly activated Steel Body and then deactivated it in an instant. Yoko tried to retreat but her other fist was still caught by Kai's hand.

After a snapping sound, Yoko managed to free herself from Kai's grip by dislocating her hand. Then, she retreated several meters away from his reach but just as her foot landed on the floor, Kai appeared without a sound right beside her forcing her to swing her fist backward.

Kai used Forceless Block and swept Yoko's legs but the moment he did so, she did a flip using her other hand as a leverage on Kai's shoulder. Then, she used some pressure on the hand rested on Kai's shoulder which made Kai's shoulder dislocate.

Using that opening, Yoko was about to land a palm strike on Kai's chest but Kai's figure momentarily vanished and Yoko's palm missed.

Kai took advantage of her momentary lapse in thinking to sweep her off her feet.

"I won."

Kai said while carrying Yoko in his arms.

"..."

Now she had to blind to not realize what was going on.

"Kenji, why are you going easy on me?"

"Well, you're a girl after all."

"That hasn't stopped you before..."

Yoko also felt the same things Arata and the others had during training. He went lighter on Umi, Erina, and Natsumi because they trained magic and not their bodies but Yoko had to take the full brunt of Kai's power during their training sessions.

After being carefully set down, Yoko looked at Kai in exasperation.

"You... forget it."

Yoko quickly left the training field. Erina went near Kai and dragged him off to the side for an interrogation.

"Kenji, what's wrong with you? You're treating Yoko like a princess, in fact, you're even treating her better than me but you lied about your reason."

Seeing Erina's questioning attitude, Kai answered in a calm tone.

"It's nothing, I'm just worried about her."

"And that's the thing, why are you worried about her so much? It's not like you've fallen for her because if you had, I would've known. Is there something happening to her that you're not telling us?"

Facing Kai's silence, Erina knew she hit the nail on the head.

"Kenji, you promised me that you wouldn't keep these sort of things a secret. Yoko is my friend, I deserve to know if anything is happening to her."

Kai pondered whether he should tell her or not for a few minutes before answering.

"It's about Emi. Something is happening to Emi and we both know that if it's about Emi, Yoko would do anything. If I was the one who brought her to the depths of despair, then Emi was the one who raised her up. It isn't an exaggeration to say that Emi is Yoko's everything right now."

Erina looked into Kai's eyes as if she was trying to go into his mind.

"And what about you?"

Emi was his biological sister after all.

"I have no right to see or interact with her but I will save her no matter what."

Seeing the resolution in Kai's eyes, Erina sighed in melancholy.

"Kai."

Using his real name, Erina took Kai's hands within his.

"That incident nearly seven years ago, it wasn't your fault. You've done more than enough, you've already saved the continent from certain doom and now you're saving the world. I know it's hard for you to accept because that was ten thousand lives but..."

"Ten thousand? No, what I'm atoning for isn't ten thousand lives."

Hearing Kai, Erina furrowed her brows.

"What do you mean?"

Facing Kai's serious eyes, she felt a bad premonition.

"Over a billion lives have been lost because of me."

Erina's eyes widened. Her magic eye was already activated and she could tell there was not the hint of falseness in Kai's words.

"No, that can't be... you can't possibly be responsible for a billion lives, there aren't that many even in the three continents! Kai, what are you talking about?!"

There was one flaw to the eyes of truth. What the target believes is true wouldn't be deemed false. Naturally, Erina came to this conclusion immediately.

Why does Kai think that over a billion lives have been lost because of him? Even if he killed ten thousand people in a day for the entire time they've been separated, he wouldn't be able to reach that many in a short amount of time.

"Kai, don't be delusional! You're being tricked!"

Facing her words of worry, the guilt in Kai's heart only increased.

"You're right, I'm only delusional."

"You..."

Kai stroked Erina's head for a bit before heading back to everyone.

Erina stared at his departing back with furrowed brows. Her eye reacted with his last sentence.

The day when the nightmares would stop, that day was far from arriving.