A firewall existed to protect an internal network from external attacks, block malicious intrusions, prevent computer crimes, and shut intruders out.
In that sense, a firewall was the boundary between internal and external networks. It monitored every packet crossing the border and stopped hostile data before it slipped inside.
It also strictly limited how much access external networks had to internal ones, while carefully monitoring any attempts the internal network made to reach outward.
In theory, a firewall could reject all malicious data, maximizing the security of whatever it guarded.
Especially for institutions as critical as the Metropolitan Police Department, physical isolation was sometimes used to ensure absolute internal security.
But—much like the systems mentioned earlier—no matter how advanced a firewall became, its essence remained the same: a program. An automated system built to sift through data exchanges.
And no program in the world was perfect. Where there was code, there were flaws. This was an unchanging truth of the hacker world.
"You're planning to disguise yourself as normal data and slip inside?"
It wasn't hard for Chen Ze to guess what Renamon intended. But he remained skeptical.
If it were him, he'd probably manipulate the authentication program for officers ranked section chief and above, sneaking in quietly without raising any alarms.
But something like "Renamon.SMS" had never been part of a human-built internal system. How was she supposed to authenticate herself—or forge an identity—past the firewall?
Gaining operational privileges was one thing. Implanting an unknown program into a police system was another entirely.
The former sometimes didn't even require a virus.
The latter was outright trojan-horse infiltration.
"Don't forget—I'm a vaccine-type Digimon."
Renamon's tone was the same calm elegance as always, unmoved by Chen Ze's doubts.
"Vaccine-type? If you weren't currently breaking into a police database, I might've actually believed that."
Chen Ze muttered under his breath. Only now did he start understanding that Digimon attributes weren't just rock–paper–scissors counters, but classifications with real, functional meaning.
"To be honest, I'd rather evolve into a virus-type. Then I wouldn't even need stealth—I'd just break straight in."
The implication couldn't be clearer: Renamon vastly preferred brute-force cracking to careful disguise.
"Enough talk. Let's go."
Before the words finished leaving her mouth, Renamon swept Chen Ze along and charged straight toward the firewall.
In an instant, a spark of electricity flared across the massive dark wall—and the two of them slipped inside as effortlessly as bubbles dissolving into water, as if they had always been part of the firewall's architecture.
And in theory—this wasn't wrong.
Vaccine-type Digimon were, by nature, anti-virus programs—living firewall extensions.
Except this time, the "Renamon.SMS" antivirus wasn't hunting malware at all.
It was hunting surveillance footage that threatened to expose them.
A good antivirus that never causes "collateral damage" isn't a real Digimon.
No issues there!
...
Tokyo Metropolitan Police Department, Nerima Ward Branch – Surveillance Center.
The officer on duty, tasked with watching the feeds for the entire Hikarigaoka area, yawned miserably.
Perhaps because electronic surveillance was still a new concept, departments across Japan had indeed established surveillance centers as ordered—but no one treated them seriously. The workload was light, the responsibility unclear, and no senior officer cared much for it.
If Officer Tanaka hadn't offended his superior during the previous assignment, he never would've been dumped into this dead-end position.
To the entire Nerima precinct, being transferred to the surveillance center was basically an announcement: Your career is over.
What achievements could someone rack up by sitting in front of monitors all day?
Even in Japan—where seniority mattered—no accomplishments meant no promotions.
And this place ran twenty-four-seven. No officer lasted a full year before begging for reassignment to some rural branch office.
"That bastard… one day I'll make him get on his knees and beg me to come back…"
Half-asleep, Tanaka mumbled angrily while rubbing his bleary eyes.
Though he hated this assignment, his instincts as a policeman kept him from sleeping through an entire shift. A short nap was fine—but neglecting work wasn't.
And with shift change drawing near, he didn't want to look lazy in front of his coworkers.
"…Huh?"
Just as Tanaka stood up to check whether anything in Hikarigaoka looked unusual, his eyes went wide, and all sleep vanished instantly.
One of the street cameras for that district had gone dark. He clearly remembered it working fine earlier.
"When did it break?"
Tanaka wasn't surprised that a camera failed. It happened at least three times a month—and not just in Hikarigaoka. Surveillance equipment was new, somewhat invasive, and vandalism was common.
He was just annoyed that it had to break now, during his shift.
He could only hope this was a temporary malfunction and not an intentional act. If someone had actually smashed the camera, he'd be busy for days.
"If I catch whoever's sabotaging cameras, they're done for…"
Muttering to himself, Tanaka casually walked toward the main server storing the surveillance archives.
All recordings before the camera broke were stored there. Reviewing them would reveal exactly how the camera failed.
But as he approached the machine, something unexpected happened—the server, which should have been in sleep mode, suddenly whirred to life.
Even stranger, the main display was filled with rapidly scrolling code—far too fast for any human to read. It looked as though the computer was autonomously resisting some kind of unknown attack.
"What…what on earth is going on…?"