“What a wonderful city!”

“I’m glad you think so,” Rio replied, a look of genuine pride and confidence on his face—not just polite words.

“I was thinking how beautiful it is. I couldn’t wait to walk around here.”

That was why I had worked so hard to get through the unfamiliar training. I couldn’t contain my excitement. My body felt so light I wanted to just take off running.

From outside, the Nexus was far more massive than I had imagined, connected at its base to the surrounding buildings and what seemed to be a station. Between the organically intertwined structures, clusters of diverse plants thrived, creating pockets of forest throughout the area.

“And it’s so quiet…”

With the Nexus at its heart, this had to be the center of AO. People walked toward the station, families relaxed in the plaza—everywhere I looked, citizens were spending their time freely. Mobility vehicles glided along the roads, while bicycles zipped past them. Many people came and went from the Nexus itself. Yet despite all this activity, a pleasant stillness enveloped the city.

Cherubim, which had surprised me inside the Nexus, stood out here in AO as well. They seemed to serve not only as monitors, but also as signals, signs, and information boards—handling all visual output functions. The buildings ahead were no exception; their walls were covered with Cherubim displaying various images. By changing the surface configuration in response to the climate, the structures could regulate indoor temperature without relying on air conditioning.

“It’s a beautiful city. But… not sterile, not cold. I don’t know, I just can’t find the right word…”

Once Rio finished his explanation, all I could hear were the whispers of the trees and the gentle voices of passersby. I thought I could even hear the murmur of a stream somewhere. There was something clearly different from the cities in the world I came from, but it was hard to describe. When I glanced at Rio, he was watching me with a gentle smile. Was I imagining things, or was there a quiet expectation in his gaze? A gentle stillness, tinged with a touch of tension. I felt like I’d known this sensation before, even in my previous world.

“A library… It’s like the whole city is a giant library.”

At my quiet murmur, Rio’s voice brightened.

“I see. Tell me more.”

“It’s not just the silence. In a library, all kinds of people are doing different things, right? Everyone’s reading books, but all different ones. Some are studying…”

Rio listened silently to my clumsy explanation.

“They’re all in the same place, but it’s like each person is in their own world.”

“Their own worlds… Like the worlds within stories, perhaps?”

“Exactly. And nobody fights over books. If the book you wanted isn’t there, you just find another one. It seems like everyone’s doing the same thing quietly, but in reality, they’re all doing something different. That kind of space, that sense of comfort… That’s what came to mind. I can’t explain it well, but…”

"You’re into books, huh?"

I nodded silently. I did. Books never forced choices on me.

“Hey, what do you think about a library that only has one book? Would it still be a library?”

“What…? Of course not.”

“Right. Then what if there were lots of books, but only one person to read them? Or if there were only many copies of the same book—is that still a library?”

If there were books but no people, it would be an archive. If it were all the same book… that wouldn’t mean much. It’s because there are different books that different people come. It’s a hard question. What are the essential elements that make a library a library? A variety of books. But what is a book? Text on paper, information. Stories passed down for centuries, organized knowledge. A collection of countless distinct things that form a unified whole. Classification. Order. Harmony.

“Harmony…?”

At my unconscious whisper, Rio’s expression softened.

“A beautiful word. Yes, here, all citizens maintain order so naturally, without force. They live in harmony.”

I had meant the blending of light and sound, nature and technology—but Rio’s voice held excitement.

“You mean people are in harmony? Not just the city or its structures?”

As I asked, I looked down and noticed light scattering across flowing water at my feet. Was it a waterway? Water ran alongside the white, stone-like path, and I realized the sound of the stream had come from here. About a meter wide, these waterways were placed all around the city, branching like leaf veins. At intersections, the sound of rushing water grew stronger and mingled with the rustle of trees and the gentle laughter of children. When Rio looked toward the sound, a toddler, around three years old, waved at us.

“Exactly. The harmony you feel in the city can’t exist without the harmony of its people.”

Harmony… of people. I looked around. The people walking by didn’t look any different from those in my old world. I tried to read Rio’s intentions, hoping to find some clue in the city itself.

“It’s hard to see harmony among people with your eyes. You only notice it when it breaks…”

He waved back at the child, who wore a milky-white band on their arm—just like everyone else.

“You sensed AO’s harmony through the city itself. That’s impressive. It means the city was right to choose you. I’ve always believed that.”

Rio resumed walking, his voice full of joy. It wasn’t the answer he had hoped for, perhaps, but I didn’t mind being praised by him.

“Harmony among people, huh…”

Still, I felt slightly disappointed. The serene, peaceful city—I’d assumed it must be supported by some cutting-edge technology or complex system. But maybe that wasn’t the case. I stopped walking. The water in the canal sparkled, reflecting light from the Cherubim. Looking closer, I noticed the waterway, running like veins throughout the city, wasn’t just a simple channel.

“This water… it’s fascinating.”

The white path, flanked by lawns, gleamed with a dull luster from being polished by the flowing water. There were no obvious grooves on its surface, just faint depressions, barely visible unless you looked closely. The water followed those dips, curving and spreading, then narrowing again. The shapes and depths of the indentations weren’t uniform, and though the water occasionally seemed about to spill, it never did. I let out a quiet breath of awe. Stone and water. Stillness and motion. Hardness and formlessness. Permanence and transience. Opposing forces woven together—this scene felt like the embodiment of harmony. Maybe these waterways were the symbol of AO. The flowing water carried a sense of tension, but also a certainty, as if it knew where it was going.

“I could watch these waterways forever. Even more than the Cherubim or the Beings.”

I crouched down and touched the water. The stream stole the warmth from my fingertips, rippling gently—but even as I submerged my hand, it didn’t disrupt the flow. I felt slight resistance, but nothing changed downstream.

“It’s colder than I expected. My fingers feel kind of strange…”

That was when I felt it—a shiver that had nothing to do with the cold. A gaze? I stood up abruptly. The people in the park were going about their business as before—joggers, cyclists, an old man reading on a bench. No one was looking at me. What was that chill?

When I looked down, I realized I’d stepped onto the grass. The meticulously trimmed lawn around the canal was clearly meant to be untouched, and yet I had disturbed it. I quickly stepped back, revealing the dark soil underneath. I was the only one standing on the grass. Embarrassed and slightly anxious, I hurried over to Rio.

“There wasn’t a sign saying I couldn’t step on the grass…”

I offered a lame excuse, but Rio just looked at me with a smile, saying nothing. My face flushed with shame, and the words tumbled out without much thought.

“I don’t know, I just… got this chill. Like I broke the harmony. Like someone was watching me… even though no one was.”

Was it just my imagination? I looked around again, but no one seemed to notice or care. I glanced back at the waterway. The grass was still trampled in the shape of my footprint. It hadn’t been a hallucination. Without that strange sense of being watched, I would probably still be sitting there. So then—who had seen me?

“…Could it be… the city?”

The air was still calm and silent, but that very silence now felt eerie. In the world I came from, I never noticed things like the sound of trees or the flow of water. Instead, I heard car horns, train noises, and… what else? I couldn’t remember. But suddenly, I found myself missing the chaos of my old world just a little. As I tilted my head, Rio said with a laugh:

“AO isn’t some totalitarian regime. We just maintain the waterways with nature’s help. That’s all. We don’t force any kind of flow.”

“Maintaining the waterways, huh. Sounds nice, but isn’t it just guiding everyone in the same direction?”

That unplaceable chill… The way I felt before and after it was so different, it was like my feelings toward AO had completely reversed. My question had a bit of an edge, but Rio replied with a chuckle:

“It’s quite the opposite… Look at these waterways. They’re not perfectly straight. They curve gently, widen and narrow, all to allow the water to flow freely at every moment. Conflict arises when everyone tries to flow in the same direction.”

“Isn’t it the opposite? If everyone flows the same way, there’s no bumping into each other, no conflict.”

“What did you feel when you touched the water?”

“Huh? Oh, well…”

I looked at my damp palm. Water slipping through my fingers, flowing freely through the city like a living thing.

“Freedom, maybe. Circulation. Or life…”

“The AO system is a lot like this flowing water.”

As I wiped my hands on my clothes, I listened to Rio’s voice.

“The water isn’t being forced along a rigid path. It just naturally follows its course, yet keeps this shape. People in AO are the same. Everyone lives freely, and still, this harmony exists.”

“AO is the waterway. And people are the freely flowing water.”

“Exactly. AO is just the riverbank, supporting the flow of its citizens. But those riverbanks are designed to follow the water’s course. The citizens are the ones driving the movement.”

The white waterway stretched out, overlapping in my mind with the view of AO I had seen from the 40th floor of the Cherubim.

“Everyone moves naturally, as they wish, in harmony. Each person understands their role, and cares for others. It’s like…”

He stopped, unable to find the right word. What was it like? A structure that forms through the harmony of different roles, each unique. I felt like I knew such a thing, but couldn’t quite grasp it. Unable to find the answer, I let the thought go and stared into the water reflecting AO. Rio’s words settled into my mind. Beyond this seemingly perfect cityscape, I felt something complex hidden beneath. But I didn’t feel like digging deeper. Like the gently flowing water, my doubts dissolved on their own. Rio narrowed his eyes at the distant, shimmering Cherubim.

“The chaotic outside world is like a river without banks. Floods, or overly rigid channels, are the furthest thing from harmony.”

I gazed at the waterway—beauty born from the unshaped flow of water.

“In AO, the harmony between people and society is something designed. Here, everyone acts on their own will, and still finds space to care for others…”

Rio began walking again. Up ahead was a large fountain, seemingly the source of the waterway in this district. As we approached, the white channels converged, the sounds of streams layering over one another.

“Uncontrolled water flow is one of nature’s greatest threats. I think the same applies to people. Water that doesn’t fit in its channel can cause disaster. You can’t dam it forcibly, nor can you just let it erode the land. In your society, didn’t differences in beliefs often lead to conflict?”

“There were places where differing beliefs weren’t tolerated.”

"That's probably true," 

Rio said, his gaze drifting far off, as if contemplating something beyond AO.

"The water in these canals flows so freely, without any control. And as long as it keeps flowing, it will never dry up."

"But long ago, before societies were even formed, wasn't humanity freer?"

"When people are free, conflict arises. In truth, our tolerance wasn't infinite. It led from division to conflict, to war. And when power was established to control things, individuals were lost. The society you're talking about is that kind of model. Both types of society are still in effect outside of AO. I think people continue to suffer."

"Yes. My world... 'the outside world' was like that too."

"The method to overcome those things is what AO has found."

"So, the answer is harmony, then?"

I stopped walking and stared into Rio's eyes. The faint sense of unease that had lingered moments before was gone now. Rio nodded and continued.

"I think you'll understand if you stay here a bit longer. In AO, there's no need to force yourself to change. You just have to let yourself flow with the current, naturally."

"Flow with the current, huh..."

"This has always been a city of water."

As Rio said this, a stream of water shot up from the fountain, soaring into the sky.

The gazes of those around us turned toward it, and I looked up as well. The mass of water, rising about 10 meters high, burst apart in the air and rained down as light particles. I squinted, shielding my eyes from the sunlight.