Suddenly, a bright light enveloped Zoro, and the next thing he knew, he was standing in a strange castle. The demon slayer world was nothing like he had ever seen before.

The castle was a labyrinth of rooms, each one more distorted than the last. It was called the Infinity Castle, and it was Muzan's lair.

Zoro quickly learned about the mission. He was to aid the demon slayers in their fight against Muzan, the first and most powerful demon.

Suddenly, Zoro felt a familiar presence. It was Rengoku, resurrected and back to fight alongside the demon slayers.

Another presence emerged, Yoriichi, the legendary demon slayer. He too had returned to aid in the battle against Muzan.

The trio prepared for the battle, their resolve unwavering. They knew they had to defeat Muzan and bring peace to the demon slayer world.

The battle was intense, with Muzan proving to be a formidable adversary. Yet, the trio fought bravely, their combined strength overpowering him.

Zoro, with his swords, cut through the demons with ease. His swordsmanship skills were unparalleled, his movements swift and precise.

Rengoku, with his flame techniques, scorched the demons, reducing them to ashes. His unwavering spirit shone as brightly as his flames.

Yoriichi, despite his age, was agile and skillful. His demon slayer techniques were a sight to behold, striking fear into the hearts of demons.

The fight raged on, the trio pushing Muzan to his limits. They were relentless, determined to end the reign of the demon king.

Muzan, however, was not about to give up. He retaliated with a powerful attack, attempting to take them down.

Despite his efforts, the trio stood their ground. They parried his attacks and retaliated, their spirits undeterred.

The battle was fierce, the castle shaking with the intensity of their fight. Yet, the trio remained resolute, their determination unwavering.

The fight seemed to last for an eternity. Their strength and resilience were tested, but they refused to back down.

Finally, the tide of the battle turned in their favor. Muzan's strength began to wane, his defenses faltering.

Zoro delivered a powerful slash, cutting through Muzan's defenses. It was a critical hit, forcing Muzan to retreat.

Rengoku followed up with a burst of flames, searing Muzan and further weakening him. His fiery spirit was unyielding.

Yoriichi, with his precise techniques, delivered the final blow. Muzan was defeated, his reign of terror finally brought to an end.

The castle, once a place of fear and despair, was now filled with a sense of victory and relief. They had finally done it.

The demon slayer world was now free from Muzan's tyranny. It was a victory not just for them, but for everyone who had suffered under Muzan's rule.

Zoro, Rengoku, and Yoriichi stood victorious. They had fought bravely, their combined strength and determination bringing an end to Muzan's reign.

The trio had not only saved the demon slayer world but also created a new era of peace and prosperity. Their names would be remembered for generations.

Despite the victory, there was no time for rest. Zoro knew he had to return to his world, his mission in the demon slayer world complete.

With a final farewell, Zoro was enveloped in a bright light, and in an instant, he was gone, leaving the demon slayer world behind.

Back in his world, Zoro couldn't help but reminisce about his adventure. The battle in the Infinity Castle would forever be etched in his memory.

The memory of Rengoku and Yoriichi, the brave demon slayers, would remain with him. They were warriors he was proud to have fought alongside with.

Zoro knew he had made a difference in the demon slayer world. He had helped bring peace to a world plagued by demons.

As he resumed his journey in his own world, Zoro carried with him the memories of the battle. The experience had made him stronger, his resolve firmer.

The tale of Zoro's adventure in the demon slayer world would live on, a testament to his courage and strength. His legacy was truly legendary.

And so, Zoro's journey continued. With each step, he carried with him the spirit of the demon slayers, their bravery and determination inspiring him.

The Battle in Infinity Castle was not just a victory for the demon slayer world, but a testament to the strength and courage of warriors like Zoro, Rengoku, and Yoriichi.

Their story was a beacon of hope, a reminder that even in the face of darkness, light will always prevail. And for Zoro, it was an adventure he would never forget.

For him, it was a battle that tested his strength and resolve. But more importantly, it was a battle that taught him the true meaning of camaraderie and courage.

And so, as Zoro continued his journey, he knew that he was not alone. He carried with him the spirit of the demon slayers, their courage and determination fuelling his own.