The inquiry arrived the morning after Mio finished the map of the root.
Mikoshiba set the printout on Mio's desk. A formal investigative inquiry, under the name of the head of the prefectural police Cybercrime Division.
"Here it is," Mikoshiba said. "Because you drew the map and the structure became visible, the police are clear now on 'what to ask for.' The targets of the inquiry are written out with pinpoint precision."
Two things were being requested. One was the information Makoto's engine had detected: the scam accounts, the IPs, and so on. The other was the map of the root, the analysis of the money's choke points. And this document was not a one-way street.
"Both directions," Mio said, tracing the items on the document with her finger. "In exchange for handing over my analysis, I formally receive the victims' data. Personal information under real names doesn't come to me without this document."
"What's your reason for wanting the victims' list badly enough to go that far?" Mikoshiba asked. "You've already drawn the perpetrators' structure in full, haven't you?"
"What I drew is only one side." Mio indicated the map of the root with her fingertip. "The ads, the bank accounts, the infrastructure—all of it is the skeleton of 'the side doing the shooting.' But where it hit, and whom—that isn't on this map. I haven't once looked at the side that got shot."
"So you'll match it against the actual damage."
"Whether the picture of the shooters really is a picture of people being shot. Only by overlaying them can you confirm it." Mio set the document down. "A map of only one side is still just half."
Mikoshiba smiled faintly, as if reassured.
Mio overlaid the victim data handed down from the police onto her own map. The side that shot, and the side that got shot. At first she meant it only as a check of her answers, but the way the data fell was clearly strange.
"...It isn't scattered," Mio said, staring hard at the screen.
"Isn't scattered?" Mikoshiba looked up.
"If it were indiscriminate, the ages and interests of the people who got caught should be all over the place. The more shots you fire, the more it scatters." Mio redistributed the victims along axes of age and region. "This is clustered."
Age, region, interests. Data that should normally have spread in every direction like the roots of weeds was drawn together without the slightest gap, forming a geometric mass. Like a topiary that a craftsman had painstakingly clipped.
"It could be a bias in the ad delivery," Mikoshiba said, as if checking. "Maybe the scam side just scattered them targeting ad slots that reach wealthy older people, say."
"That was my first suspicion too." Mio opened another window and lined up next to it the distribution of the population the scam ads had been shown to. "If the delivery were biased, the mound of 'people who saw the ad' and the mound of 'people who got caught' should overlap in the same shape. But—they're offset. The net they cast is spread out normally, but only the prey is gathered at one point. From among the people it reached, only the hits are being picked out."
With that, the discrepancy between the two distributions became plain for anyone to see.
"It's too perfect. There's no way this is a shape that grew naturally. This is—the trace of a sniper."
Aya and Mikoshiba peered at the screen.
"It's a 'garden,' designed in advance," Mio went on. "Someone is passing along, behind the scenes, a 'list' that sorts out the people easy to deceive. They line up only the targets most likely to be hit and fire into them with precision, which is why it lines up this neatly. ...It's too skillfully done."
"Let's pass word along to the police," Mio said. "That there must be a list for the sorting somewhere. Also, by tomorrow the branches will have grown back onto new infrastructure. So we'll keep running the net inside Makoto and hand the updated analysis to the police each time. We hand over a map that keeps being drawn."
Mikoshiba understood what that meant at once. He passed along to the police contact, all together, the findings of the analysis and a promise of continued information sharing going forward.
"That's good," Mikoshiba said, coming back. "A platform that stands for 'zero scams' and keeps putting out analysis through a public-private partnership. It'll be a fine track record."
Mio shrugged, uninterested. "I just built the system. Collecting the trust is your territory, isn't it?"
Mikoshiba set a plate he had prepared at some point beside Mio's hands. A seasonal limited-edition dish that should have been sold out for three days running.
"It's an expense," Mikoshiba said shortly. "The CTO's judgment accuracy is a company asset."
Mio picked up her fork, eyes still on the screen.
"...Well, it's not bad."
Mikoshiba got up, satisfied, to make coffee. To his back, Aya murmured in a voice too low to hear.
"(A sold-out dish, procured from somewhere with three days' worth of tenacity... And to settle it all with the single word 'expense.' Master Mikoshiba, today again your one-sided love is splendidly in the black.)"
"So, how did you notice? That too-perfectness," Mikoshiba asked.
"When I overlaid the map and the damage, the way it clustered was skewed. Once I ruled out the delivery-bias line, what remained was 'sorting.' That's all."
Mio moved her fork. Why a dish that should have been sold out was here—she never stopped to think about the reason.
Some time after that, members of the fraud ring were arrested in a sweep. The news coverage was restrained, flatly reporting the number of low-level members picked up and the amount of damage. Nowhere in the articles did Sigma's name appear, or anything about the map Mio had drawn. Only, the lineup of the bank accounts tied to the arrests overlapped neatly with the nodes Mio had marked as "the crux of the money." A single map, its name never mentioned, had pointed correctly to where the doors were.
"They didn't get all of them, did they," Mio said, glancing sideways at the article.
"No, they only picked up the low-level ones," Mikoshiba said.
"I thought so. The ones at the top are anonymous, and if they're based overseas, the police can't go in. Give it a while, and they'll spring up with different faces. That's how the other side is designed. But if it deters them and minimizes the damage, that's enough."
On the map of the root Mio called up in the corner of her screen, several of the low-level nodes caught in the sweep had sunk into gray. But within a few days, from the position of the formless hub where Mio had once glared and said "there's something here," new young lines began to sprout again. As if, in place of the severed tail, it were taking its time reconnecting a different set of nerves.
"They only cut off the lizard's tail. The system itself is still alive."
Behind the low-level nodes sunk in gray, the center that couldn't be named was stirring again.
The police had walked over the structure and caught people.
But that list of people easy to deceive, used to make that "too-perfect garden"—where was it coming from?
Only that cold unease remained, quietly, in Mio's hands.
Outside the window, dawn was about to break.