“Found it! I now fully understand your Infinity Castle, Nakime!” Through extensive perception of the Infinity Castle's changes, Lixing had grasped its rules.
Specifically, the Infinity Castle was somewhat akin to a Mobius strip, looping back to the starting point no matter how one traversed it.
Lixing, a genius scientist comparable to the inventor Grey Wolf, excelled in battles of intellect.
Without hesitation, Lixing flew according to the pattern of the Infinity Castle's door openings and closings, quickly arriving at Nakime's location once more.
“Star Lord!”
“Mr. Lixing!”
Mitsuri and Tamayo cried out simultaneously, their eyes unable to conceal their joy. It was good that Lixing was unharmed.
“I’ve kept you waiting. Let’s go together.” Lixing drew his sword and slashed in mid-air. The wooden door before him could not withstand Lixing’s blade.
Nakime seemed aware of Lixing’s power and strummed her biwa again, attempting to teleport Lixing away.
However, Lixing, who had just been confined by several doors, suddenly reappeared on Nakime’s other side.
“Nakime, I have seen through your Blood Demon Art!”
“Snow Breathing, Final Form: Absolute Zero!”
Lixing raised his hand and froze the nearby doors and windows. As Lixing advanced, the frigid ice gradually spread towards Nakime.
“Serpent Breathing, Fifth Form: Twisting Snakes!”
“Love Breathing, Third Form: Cat-Love Shower!”
“Blood Demon Art: Thorn Technique!”
Iguro and Mitsuri followed Lixing’s attack, while Tamayo provided remote support. You might ask where Yushiro was? He was, of course, behind Nakime.
Earlier, when Lixing was blocked by Nakime’s doors, Lixing had thrown Yushiro into a door facing Nakime, telling him that if the door in front closed, a door behind would surely open, and by charging through, he could reach Nakime’s rear.
Nakime strummed her biwa, blocking all their attacks, but still couldn't stop Lixing’s freezing. In an instant, Nakime's lower body was encased in ice.
Yushiro suddenly appeared behind Nakime and pressed his hands against her head.
“Blood Demon Art: Blinding Sight!”
At this, Nakime could no longer move and was completely controlled by Yushiro.
Iguro raised his hand to strike, but Lixing quickly stopped him.
“Nakime cannot be killed for now. We need to trap the demons within the Infinity Castle. If the Infinity Castle collapses and Muzan escapes again, we might never find him.”
Lixing explained the situation to Iguro. Keeping Nakime alive was better than killing her. After Muzan was dealt with, his subordinates would likely perish along with the Demon King due to the blood curse; Muzan was that kind of person.
“Yushiro, you control Nakime. Miss Tamayo, please stay here to protect Yushiro. I will complete our cooperation.” Lixing instructed everyone on the plan, while telling Iguro and Mitsuri to support other Pillars. He himself needed to find Douma.
“Star Lord, please be careful on your own. I wish you strength in battle,” Mitsuri said, looking back at Lixing as they parted.
Iguro’s heart ached seeing Mitsuri so close to Lixing, but now was not the time for such feelings; slaying Muzan Kibutsuji was paramount.
“Kanroji, let’s go,” he commanded and then left Nakime’s vicinity with Mitsuri.
…
Over with Zenitsu Agatsuma, a demon wielding a sword was fighting him. Both were using Thunder Breathing, but one only knew the First Form, while the other knew all forms except the First.
“Thunder Breathing, First Form: Bolt Flash Sixfold!”
“Thunder Breathing, Second Form: Distant Thunder!”
Ultimately, Zenitsu was outmatched and wounded by the newly appointed Upper Rank Six.
“Kaigaku, you’ve eaten many people, haven't you? You’ve lost all sense of good and evil. You’re not worthy of being Grandpa’s disciple!” Zenitsu roared at Kaigaku.
Kaigaku glared at Zenitsu with disgust. “You weakling, what right do you have to speak to me? As long as I can live, I will make others look at me with respect! It's with this belief that I've lived until today!”
“You pathetic creature, no matter how much you improve, you can never achieve power comparable to an Upper Rank. That old geezer actually made me and you, a weakling, inherit Thunder Breathing together. You and your master both deserve to die!”
“Good and evil? Those who accept me are good, and those who don’t are evil! I’m different from you all; I am special! How does it feel to be struck by Thunder Breathing enhanced by my Blood Demon Art? Hahaha!”
“Waste of space! Die!” Kaigaku roared, venting his past resentment and disgust for Zenitsu.
“Thunder Breathing, Sixth Form: Thunderbolt!”
Zenitsu was struck by the lightning centered around Kaigaku and slowly closed his eyes, recalling his training at Mt. Tao and the teachings of his grandfather and elder brother.
“Break through your limits and reach that supreme realm!”
As he was struck down by Kaigaku, Zenitsu seemed to hear his elder brother Lixing’s words during his fall. His mind suddenly became clear, and everything around him seemed to disappear, leaving only Kaigaku, who had become a demon, above.
“Is this the supreme realm Brother spoke of? Thank you, Brother, for still guiding me even at the end. I will definitely slay Kaigaku!”
“Thunder Breathing, Seventh Form: Fire God!”
Zenitsu lightly stepped on a nearby rooftop, concentrating all his strength into his legs, and shot upwards with speed that surpassed his limits.
Kaigaku, before he could react, had his head severed by Zenitsu.
“What happened? Why didn’t I see it? A combat technique I’ve never seen before. Damned old man, he must have secretly taught this loser a special move behind my back.” Even at the brink of death, Kaigaku continued to blame others, but Zenitsu no longer cared; such a person was not worthy of being his senior disciple.
“You’re wrong. This wasn’t taught by Grandpa; it’s the Seventh Form I comprehended and created myself. I truly wish I could fight alongside you with this move, but alas, you’re not worthy!” After saying this, Zenitsu fell unconscious, plummeting from the sky along with Kaigaku.
“Seventh Form? Impossible! You weakling, how could you possibly create the non-existent Seventh Form? You’re lying to me! Right, I haven’t lost, and you’ll also fall to your death. You’re unconscious, and falling from this height, you’ll surely die more miserably than I!”
“Shut up, you! Still putting up a brave front, how disgusting!”
A voice suddenly echoed from the sky. Lixing swiftly flew towards Zenitsu and caught him. Kaigaku’s eyes were filled with disbelief. How could someone fly? Why? Why was everyone denying him? Kaigaku would never get his answer; Lixing delivered the finishing blow, shattering Kaigaku’s head and body into pieces with a single strike, accelerating his descent into dust.
“So, you finally used the Seventh Form, did you? Back at Mt. Tao, I told you that if your body couldn’t withstand excessive speed, you'd die from internal organ rupture. I told you to train your physique more, but you didn’t listen. However, entering the Clear World was unexpected.”
Lixing placed Zenitsu in a room and examined his body. Fortunately, he had entered the Clear World at the last moment, shutting down unnecessary senses. Otherwise, that last move alone would have resulted in lifelong injuries.
“Rest well. When you wake up, all of this will be over!” Lixing gave Zenitsu medicine made by Shinobu Kocho and then left, needing to find Douma within a short time.