"It's done," Mio said, in a voice worn completely thin.
"The first-stage screening stays as anomaly detection and Bayes. That part's unchanged. Behind it, I added one more layer: second-stage screening. The AI agents read only what the first stage marked as suspect, and judge it scam, clean, or on hold."
Mikoshiba was standing behind her. "So—in terms I can understand?"
"They painted over their faces and their words and slipped through my net." Mio pointed at the red dots on the screen.
"So behind the cheap net, I put one heavy inspection room. An examiner that reads the text and the image together and judges, with reasons, whether it's a scam. If it needs to, the examiner traces back through past posts on its own. If it's a celebrity's face, it even checks whether there's permission. When it can't call it black or white, I made it leave the judgment to me."
Mikoshiba slid the strawberry daifuku he had left on the edge of the desk to just within reach of Mio's fingers. Then he took off his own jacket and draped it over her shoulders. He said nothing. There were plenty of things he might have said, but any one of them, spoken aloud, would have brought this man's pretenses crashing down. So he simply put something warm close by and made sure she wasn't cold. That was all.
"I had strawberry daifuku ready. When your sugar runs out, the accuracy of your judgment drops." That was all Mikoshiba finally said.
"...That helps," Mio said, taking the pretense at face value and pulling the daifuku toward her. Her fingertips, though, were still trembling a little. "But don't get the wrong idea. All this pulled out is 'the current branch.'"
"Branch?"
Mio didn't answer that. She just looked at the red dots on the screen, her gaze suddenly cool. She took a single bite of the daifuku and sank deep into her chair. Her eyelids were heavy. Her mind had been worn down too far to carry on with that conversation.
Dawn was about to break. The inspection room in the back that Mio had built had indeed adapted to the current enemy. That should have been enough.
For the next three days, the rebuilt net did its work in silence.
The enemy kept changing tactics. Shifting the wording slightly, swapping in different faces, spawning new accounts. But the performance monitoring caught each moment of change, and the net reconfigured itself every time, pulling out the newly sprung faces in bundles all over again. The detection rate would drop, then recover. Drop, then recover. The net Mio had made breathed in the enemy's changes like air and kept on adapting.
"It hasn't stopped," Mikoshiba said, looking at the line graph on the dashboard. A fine sawtooth line that kept starting to dip and then recovering. "So this is what you meant by 'continuing to adapt is the shield.'"
"Yes," Mio answered, cupping her coffee in both hands. "The instant they change tactics, we reconfigure too. Never pin down 'what kind of net it is right now.' That's the most solid there is."
Mikoshiba gazed at the line for a while, then the corners of his mouth eased.
"Word's starting to get around out there."
"Word?"
"There are other social networks that advertise 'zero scams,'" Mikoshiba said, leaning back in his chair. "But most of them only advertise it. They put up the sign, but whether anything's actually being stopped is another story. We really are stopping it, and keep stopping it. People who can tell are starting to tell. 'That place isn't just talk,' they're saying."
Mio looked at him over the rim of her cup. She had seen it a few times now: the "word" and "reputation" Mikoshiba talked about eventually turning into work. He sniffed things like that out and gave them shape.
"That's a management matter," Mio said shortly. "I don't really understand it."
"That's fine. That's my job." Mikoshiba laughed. "You just keep stopping them."
Mio turned her eyes back to the dashboard. The sawtooth line kept dipping and recovering as before. The net was definitely winning. Tonight, too, it was pulling out every face that sprang up.
And yet an unpleasant sensation lingered in Mio's fingertips.
"...I'm holding the line, and it doesn't feel like winning," Mio said, almost to herself.
Mikoshiba looked up. "What do you mean?"
"The faces I caught tonight." Mio pointed at the cluster of red dots on the screen. "By tomorrow, they'll be gone. This domain, this IP, this account—they'll throw them away and make new ones. Even when I pull them out in bundles, they spring back up in bundles. All I'm doing is cutting 'the current branch.'"
Mikoshiba looked at the red dots. Tonight's spoils. Spoils that by tomorrow would be nothing but carcasses.
"Cut them and cut them, and they grow back," Mio went on. "Cut one, and two come up beside it. The net is adapting. But it's only adapting. Even holding the line, it never ends. I want to deal with this a bit more efficiently."
Mikoshiba looked at her profile. A face that had spent three days glaring at the sawtooth line. Even so, her eyes alone were cold and clear as ever, fixed on something beyond the screen.
"Then what will you do?"
Mio didn't answer right away. She just looked at the cluster of red dots. She had the feeling that, behind the spoils of holding the line, there was something she still hadn't seen. She nearly caught it, and it slipped away. Only its outline remained at her fingertips.
"...I don't know," Mio said, plainly, which was rare for her. "But for now, we're keeping them out. It's not urgent. I'll think about it again when I feel like it."
Mikoshiba asked nothing more. When Mio "set something aside," it was usually because she was looking at something bigger. He knew that by now.
"All right." Mikoshiba cleared away the empty plate. "Then call it a night. The net won't stop. Even while you sleep, it'll keep reconfiguring on its own, won't it?"
"Yes. That part, at least, is well made." Mio smiled faintly.
Close to dawn, Mio fell asleep on the sofa.
Mikoshiba draped a blanket over her. Aya, watching from the shadows, laughed with only her mouth: "...Pfft."
All through the night, the line on the dashboard kept dipping and recovering. Tonight, too, the net held the line. Not a single scam remained in Makoto's feed.
Even so, a bad feeling still lingered in the fingertips of the sleeping Mio.
The branches grow back no matter how many times you cut them. As long as you cut them one at a time, you'll never catch up. Then wasn't there a way to stop cutting them one by one, and reap them all at once? Behind it all, there had to be something she still hadn't seen. Not further down the road of endless cutting, but that "something," taken whole.
What it was, Mio did not yet know.