Kai gazed at the stunning landscape with curiosity gnawing at him. "By the way, Aria, what brought you here?" he inquired, trying to keep his tone casual.

Aria's eyes widened in surprise, caught off guard by Kai's question. "Oh, I completely lost track of time and forgot to tell you my reason for coming here. I came to find you because everyone else is ready to return," she replied, her voice low and mellow.

After hearing Aria's response, Kai stood silently, lost in thought. "Let's go," he finally said. "We have to reach the village before it gets dark. Demons are more powerful at night, and we don't want to be caught off guard."

Without a word, Aria followed Kai out of the building, which had once been a botanical research lab called "BioGreen Laboratory." It was one of the few places left untouched by the Great Demon Uprising that had brought almost all of humanity to the brink of extinction. The event had destroyed almost all agricultural land, and most of the water sources had become poisonous. Survivors had scattered around the globe in search of food and water, creating small villages.

Kai and Aria had taken shelter in the lab along with a group of people from a nearby village. As they stepped out into the yard, they were greeted by Yuta, a young boy from their group. "Oh, both Mr. Kai and Mrs. Aria have returned," he announced.

Kai surveyed the group. "Is everyone here?" he asked.

"Keiji and Ava went to fill water for our journey," Yuta replied. "Everyone else is here."

Kai's brow furrowed in concern. "Aren't all the sources of water poisonous?" he asked.

"Yes, they are," Yuta confirmed.

"Then where will they fill water for the journey?" Kai pressed.

A man in his 30s called Ken stepped forward. "Since the demons attacked, most of the water sources became concentrated with high levels of their 'mana,' which is poisonous for any living being on earth to drink. However, underground water and rainwater contain very little 'Mana' concentration, which can be easily purified by anyone who knows basic purification spells. There's an underground source of water located around 10 km east of here, and that's where Keiji and Ava have gone to fill their water."

"How long have they been gone?" Kai asked.

"For around an hour, I think," the man replied.

Kai looked up at the sun. It was getting lower in the sky, and they needed to reach the village before dark. "We don't have much time. We have to leave a message and mark our trail so they can catch up with us later," he said, taking charge of the situation.