Ma En stood to one side, turning over what the neighbor had said, while sinking into the man's grief. The emotion that had broken through was something he couldn't claim to share — but it was exactly these feelings, accumulated and compressed by years, that had finally cracked open the secrecy this friend had kept so long. Ma En felt he genuinely hadn't wanted to say so much. Some force — some mechanism beyond feeling — had wanted him to carry these secrets to his grave. He had no longer been able to do it.

When he began to speak, the emotion in him was like a car with the throttle removed and brakes failing, the body barely keeping its shape, threatening to fall apart entirely at any moment. What the neighbor presented right now still had some portion of rationality intact. But Ma En felt the collapse coming — a collapse from the rational to the physical, from the mental to the foundational — and there was nothing either of them could do to prevent it.

Ma En had the odd sense, perhaps too fanciful on his part, that the large figure working in front of him seemed to burn. But this invisible fire was pale and cold — burning fiercely enough, yet looking as though it might go out at any moment.

The neighbor used his bare hands to dig a pit in the earth, used the vine-like extensions to sever branches and roots, stripping bark completely clean. While he worked, he sometimes pressed himself to the ground and put earth into his mouth, even buried his head into the pit to examine the shape of the roots, and sometimes climbed into the tree or circled the trunk — Ma En couldn't begin to interpret many of these actions. Even in a bizarre and uncanny situation like this, even though Ma En had come to accept the strange and the odd, this neighbor's behavior still astonished him, and his first instinct was: is this person's mind simply broken?

But in rational terms, the neighbor was the person who knew these monsters best — even having acknowledged there were many things he himself didn't understand — and so his actions should have some logic behind them. Ma En simply couldn't determine what that logic was. What was happening here, like everything else he'd encountered in the Room 4 Ghost Story, fell outside his common sense.

The two of them went a long stretch without speaking — one watching quietly, the other working quietly. About ten minutes in, the neighbor finally stopped. He let out a long breath, as if satisfied, shook the branches and roots and clumps of earth from his hands, and sat down heavily on a nearby stone. He pointed at the excavated mess in the pit.

"I'll teach you a simple method," he said.

"What kind?" Ma En wasn't sure what the man was pointing at.

"Identifying monsters is very difficult. When they're living as humans, most of the time they're no different from ordinary people. I won't tell you how to pick them out of a crowd — it can't be done with human senses alone. With scientific equipment... perhaps there's some possibility, but the instruments would be extraordinarily expensive and impractical to use." The neighbor explained.

Ma En tried to read ahead of him while following the instruction to step into the pit. "About how much would it cost?"

"Hundreds of billions of dollars, perhaps — if a government actually knew they existed and genuinely committed to research for isolating them from ordinary people. In practical terms, it would be on the order of discovering mass-energy equivalence, developing nuclear applications, and ultimately producing atomic weapons — that entire process. Not just money. The theoretical research, the gradual practical application, the expense of it all — a cognitive expense, an energy expense, a directional expense. If you start in the wrong direction from the beginning, you waste even more time..."

The neighbor's mood, which had been running high, dropped slightly at this point.

"Just identifying them?"

"Not even that — potentially identifying them. Whether it's actually possible, I don't know. I've never seen equipment like that."

"Fair point."

"These things, after all, can traverse the cosmos and pass through black holes on nothing but their own physical ability. Truly understanding them is enormously difficult. Human science may have reached a certain height, but in practice it's still a very long way off. When humans can navigate black holes — perhaps then they'll be able to truly understand what these monsters are."

"But by then we won't be here anymore." Ma En didn't want to pursue that topic. "What's their lifespan like?"

"Uncertain." The neighbor's voice became calmer. "When they live as humans, the lifespan they display is roughly that of an ordinary person — average for the species. But when they die in the human way — by accident or naturally — whether they're truly dying in their inherent form of existence, I can't say."

"And yet you came back." Ma En glanced at him.

The neighbor laughed — a hissing, sharp sound, full of something malicious. He turned it back: "In your view, am I a person, or one of those monsters? Do you think I'm alive, or dead right now? Do you want to end up like me? Don't worry — after August passes, you'll have your answer."

"I don't want to end up like you, friend." Ma En said it without any hesitation, without any softening in his voice.

"That's not really a matter of what you want. In the first few days, maybe you still had a choice. But a month has gone by now. You've lost your chance. You don't even remember what happened to you during that month, do you?" The neighbor was mocking him now, using a needling tone — as if this could ease something inside him. "See? I told you. You're a fool."

If keeping the conversation this way helped the man's mood, kept him steadier, Ma En didn't mind at all. This neighbor was a precious friend — the only person nearby who held so many of the secrets. His actions were clearly driven by emotion; early in the conversation he'd managed to contain himself, but now, with each small emotional outburst, the secrets were coming out of him on their own.

Like momentum.

At this point, there's no more need to prod him.

The thought surfaced in Ma En's mind.

The neighbor's view of Ma En was harsh, and his language about Ma En's future was harsher still. But Ma En didn't believe this malice-tinged harshness was false. In the worst possible case, everything the neighbor was implying could come to pass.

"What should I do?" Ma En shifted the topic again. He picked up a branch, mimicked the neighbor's motion, tilted his head sideways to look at the roots embedded in the earth, took a fistful of soil and smelled it — everything he sensed was entirely ordinary. Just earth. Just wood.

"What I'm able to do, you may not be." The neighbor only watched him, as if deliberately waiting for him to initiate before speaking. "I said I'd give you a simple method. This method won't let you pick these monsters out of a crowd of people. But it can roughly tell you whether a given tree has been made into a monster. Once you know how many trees have turned, you know roughly how many people have. You understand? The person and the tree are one — they've become each other."

"People and trees merging?" Ma En paused — it reminded him of what he'd seen in the nightmare.

"Not only trees. Trees are just the easiest to read." The neighbor paused, then said: "The bark and stripped surfaces, the roots and the soil — none of that will be useful to you. All you need to look at is the growth rings."

"Growth rings?" Ma En looked at the broken branch in his hand. "Do branches work?"

"The trunk is best — but you can't go around felling trees. You'd need tools, and it's not practical. What I'm teaching you is the simplest method."

"A trunk this diameter..." Ma En thought it over. "I think I could probably snap it."

The atmosphere went quiet. A slight tension settled in. Ma En felt the neighbor's mood shift again.

"...Are you a monster too?" The neighbor spat to one side, then caught himself and added with self-satisfied disdain: "Then again — if you weren't this strong, why would I have picked you?"

Ma En was left with nothing to say. He'd always felt himself to be entirely ordinary — but thinking about it carefully, perhaps not exactly like other people. Though as far as he was concerned, he hadn't sunk to the level of being called a "monster" by an actual monster. The neighbor — if you cut his head off right now, Ma En was fairly sure he wouldn't die from it. Whereas Ma En — a beheading would kill him, a heart puncture would kill him. Every cause of death applicable to ordinary humans applied to him the same way.

"The growth rings of the branch..." he shifted back to the subject. "Is there something abnormal about them?"

"The trunk's rings are clearest. For branches, choose ones as close to the base as possible, or ones with the most sun exposure — those receive the most nutrients and are most likely to show the rings. If there are many trees, choose ones that are over five years old — older is better. But actually it doesn't matter much; as long as there are rings at all, it works." The neighbor explained. "First, you need to know how old the tree is — how many rings it should have. I'll tell you now: this particular tree is only twenty years old. You know how many rings it ought to have, yes? In temperate regions each year produces one ring, and the boundary between rings is clear. In tropical regions the climate doesn't vary much within a year, so the rings aren't as distinct."

Ma En stared at the cross-section of the branch in the near-dark. It was far too dim to see anything, but he pretended he could, and said: "The rings... seem a bit off?"

"Of course they're off," the neighbor said. "How many rings do you count?"

Ma En ran his thumb over the cross-section, feeling the texture, the density. He guessed: "Far more than twenty."

"Hm-mm." The neighbor dismissed this casually. "It's older than the theory says it should be. You understand why?"

"You mentioned before that people and trees merge... but I can't see anything about it that looks like a person." Ma En answered plainly.

"Because the tree's rings are the tree's age and the person's age added together." The neighbor's tone became careful now. "For a branch you get slightly more error. But if you look at the trunk's rings, you'd find at least fifty. This tree is only twenty years old. Fifty minus twenty is thirty. The monster that merged with this tree — its human appearance is probably somewhere in the range of thirty to forty."

"That's all?" Ma En was a little surprised. Could a judgment really be this effortless? The neighbor had said the method was simple — but this simple?

"That's all. Once you know the principle, it's straightforward. The difficulty is ever arriving at the principle in the first place." The neighbor said evenly. "First you have to think of it. Then you have to do it. For human beings, those are the truly hard parts."

"...That's rather philosophical, friend." Ma En smiled. He'd always had the sense this neighbor was no ordinary person — but even having become what he was now, the man was still working out the logic from a human angle.

"It's just lived experience," the neighbor said dismissively.

But human lived experience, all the same.

Ma En thought this without saying it.

"Incidentally — in the nightmare, I saw something far more obvious. Human bodies merged with plants, very explicit." Ma En said.

"Don't take everything in the nightmare as real. The things in there are even more distorted than the things out here — it's abnormal, and not objective. At least not as objective." He seemed to hesitate slightly as he said this, making Ma En feel he wasn't entirely confident in his own view. Sure enough, he shifted: "But don't disbelieve it entirely either. Treat what appears in dreams as suggestion — not literal reality."

"So the most basic outward sign of these monsters, in the real world, is the trees — and maybe other plants — showing unusual ages?" Ma En confirmed.

"Yes." The neighbor immediately added: "That's my view, anyway."

"I've been wondering," Ma En said, setting down the branch. "Doesn't doing what you're doing draw their attention?" He gestured at the damage around the tree. "This tree — which is apparently one of them — and what you've done to it."

"What I've done barely qualifies as a tickle to them," the neighbor said. "Trees are mostly slow to respond, aren't they? If it were you doing this, they'd be quite sensitive to it. But with me here, they feel safe — like they're asleep. It's as if someone on a crowded train bumped your shoulder — would you even register it? What I'm doing to them is several hundred times lighter than that."

"Because they think you're one of them?" Ma En tested.

"Probably part of the reason." The neighbor was unbothered. "Like someone jostling you on a packed train — you'd barely notice. That's the order of magnitude."

Ma En didn't speak. A moment later, the neighbor continued: "Remember this, my friend: this method can let you identify some monsters, but not all of them. Not every monster merges with trees. Many will live out their entire existence in human form. And remember — if any of the tree-merged ones wake up, run. Even if you can currently snap these trunks — once they become monsters, your brute strength won't be effective anymore."

"When would they wake up?" Ma En didn't doubt what the neighbor said. Both the neighbor's own nature and the behavior of the burning tree in the nightmare left him certain: human force could not hold against them, not without something significantly more powerful.

"Someone calls them and they wake." The neighbor said. "Keep my words close, friend. To deal with Matsuzaemon, be ready to face these monsters."

"If I set a fire and burned this entire grove?" Ma En turned to face the neighbor directly — that immense body, those sharp eyes. "What then?"

"If I could have, I would have done it already." A snort. "No point. You can't destroy one side without destroying the other simultaneously. Burning the trees without killing the people at the same time does nothing. And if you burned the grove — the best-case outcome would be those monsters going berserk." He paused. "Look at this forest. How many trees? How many monsters? Not a few hundred at minimum — more likely a thousand or more. The last thing you want is thousands of sleeping monster-humans waking up in human form and starting a war. They have outside resources too — even if a crowd of tens of thousands rioted and then were completely wiped out by the military, it wouldn't do their overall numbers any real damage."

So it's not that simple.

Ma En thought, with something like regret.

"Stop considering unrealistic approaches. They've been on this planet through every mass extinction. Never doubt that they have more than sufficient mechanisms to ensure their survival. Whether they integrated into a dinosaur society or a human one makes no difference to them. The basic genetic material constituting them, the basic rules by which they operate — these contain something built for the cruelty of cosmic scale. Human cruelty compared to cosmic cruelty isn't worth mentioning. Adaptation, integration, growing alongside a host civilization, and remaining capable of separating from it at will — in a certain sense, they are freer than humans."

"By what you're saying, humanity has no way to deal with them at all?" Ma En asked.

"Turn the question around: why should humanity deal with them? They've been living alongside us since before humans existed. Their bloodlines are already threaded through human bloodlines. The self-sustaining order of human civilization is itself the best response to their existence — a harmony formed over millions of years of evolution. When they're not causing trouble, going after them would make you a fascist in the eyes of the world. Do you want your head on a block?" The neighbor went on. "Human culture and civilization have reached a point where you can't simply treat these creatures as existential enemies."

Hearing this, Ma En felt something release in his chest. Because this degree of integration actually confirmed, in a roundabout way, the truth of the neighbor's position: killing Matsuzaemon was enough. Kill the primary cause and compromise on the rest — that was entirely in the human tradition. Human society had always advanced through compromise, and things that went too far to the extreme tended to have short lifespans.

And regardless of what he worried about, the things he could actually do were limited. Killing one monster — perhaps achievable. Killing an entire population of monsters living among humans identical to humans? That was genuinely beyond imagination.

"I'd also like this to be as simple as possible." Ma En said this with sincerity.

"Simple in concept, yes. But..." The neighbor paused. "How to actually kill Matsuzaemon — that is the real question."