Digimon Underground

<Virtual Paradise>

Welcome to the Digimon Underground
Fergus Halliday
Nov 14, 2023
bullet12 min read

Digimon’s take on Tamagotchi might have a smaller screen, a tiny processor and a fraction of the memory as the Nintendo Switch, but the two have more in common than you might think.

Even if they’re rarely seen as such, virtual pets like these are a type of video gaming console. They’re just a very limited one. There are plenty of other differences of course, but one of the more understated ones is the dynamic that the consumers buying this hardware have with the company that manufactured it.

Walking out of JB Hi-Fi with a Playstation 5 is only the beginning of your relationship with Sony, but the link between you and Namco Bandai only really lasts as long as it takes you to pay for one of the company’s virtual pets. For many, the end of that nanosecond-long bond is the start of something else entirely.

Digimon and virtual pets are over twenty years old. The fad has faded, but the fandom stuck around. More than that, it’s given the gadget a new life.

This world of Digimon modding is almost as old as Digimon itself.

"If we include things like swapping shells and frames, then it’s likely been around since the beginning of Digimon,” a member of the virtual pet community who goes by the pseudonym Humulos told me.

Today, Digimon is one of those 90s pop culture monoliths that encompasses everything from toys to anime to video games to fashion. Back in 1997 though, it was just one thing.


It’s easy to overlook or forget, but the franchise was originally a spin-off of Bandai’s Tamagotchi brand. At the time of Digimon’s conception, the craze was in full swing. Some estimates from the time suggest that Bandai sold somewhere around 70 million Tamagotchi units during this period.

It didn’t take long for the company to try and replicate that success. More specifically, Bandai wanted to repackage the tech powering Tamagotchi into something with a more ‘masculine’ bent. That desire to move beyond the female-skewed audience that the Tamagotchi had tapped into led to the creation of the first Digimon virtual pets.

Like Tamagotchi, the first generation Digital Monster was a toy that let you take care of a virtual pet in real time. But where the former was more open-ended, Digimon was geared around the thrill of competition.

Play Video

Instead of mini-games, Digimon had battles. Being a good owner led to your pocket-sized monster becoming more powerful, which made it more effective at fighting other monsters. It wasn’t just enough to feed and train your keychain-bound critter anymore. You wanted to have the biggest and toughest monster on the block.

This tweak to the formula proved a commercial hit for Bandai. It also gave rise to the first era of modding as enthusiasts and technically-minded fans quickly took Bandai’s virtual pet into their own hands.

These early modifications weren’t nearly as ambitious as what could come later, but the barrier to entry wasn’t all that steep either.

“The devices are very easy to take apart, and doing something like changing buttons or swapping out one board for another is a pretty straightforward process,” Humulos explained.

By comparison, more advanced modifications like changing the clock speed or roster of a given virtual pet were more difficult. Sometimes, your ability to mod a virtual pet even depended on where you lived.

“Those sorts of modifications didn’t really exist at large in the US, where I live in the early days, or most of the world for that matter, simply due to how limited the distribution of Digimon devices was,” he explained.

Fortunately, that didn’t stop fans from trying to peel back the layers and tinker with the toy that had ignited their shared passion.

Another member of the virtual pet community, who goes by the pseudonym BluDragon, explained that “Digimon is uniquely predisposed towards the virtual pets being modded” for a number of reasons, the least of which is the fact that the premise itself is “steeped” in the culture of the 90s.

Digimon devices connected to a laptop

Hackers, computers and the early internet infect not just the very concept of a virtual pet but also the plots of countless Digimon narratives, from the original video animation “War Games” (which later made its way to Western cinemas as part of 2000’s Digimon: The Movie) to the recent Cyber Sleuth video games.

Again and again, the franchise asks fans to imagine a world where they had a virtual pet that existed within their computer. Can you really blame them for trying to make it a reality?

“You just finished playing a video game that told you about how cool it would be if you were to be a hacker who connected it to your computer. Your first instinct is to find a way to connect it to your computer, right?,” BluDragon said.

Humolos has his own hypothesis about why fans modify V-pets. Most mods add something to the experience. Some are even considered must-haves by fans like himself.

“I think everyone with a Digimon Pendulum Ver.20th should mod it to unlock every egg, and likewise everyone with a Vital Bracelet BE should install the firmware enhancements that improve quality of life on the device,” he said.

It doesn’t hurt that getting into V-Pet modding is a lot easier than it used to be. These days, the internet is littered with modding guides, videos, forums and wikis aimed at helping those looking to make the hardware their own.

Humulos himself estimates that he’s written something like 50,000 words on the topic.

Asked how big the V-pet scene is, he conceded that it’s hard to say due to the disparate nature of the communities involved.

Play Video

There’s no single place on Reddit, Discord or the internet that has all the information that a prospective Digimon modder might need. The Digimon 0NL1NE community has a ton of resources for those looking to battle while the Digitama Hatchery is geared towards those looking at cosmetic mods like sprite swapping.

“There are a few other servers too for more specific purposes, and as for how large the community is, it’s a mixed bunch of modders and non-modders, so hard to say exactly,” Humulos explained.
“For people that have used a mod, certainly several hundred have at least dipped their toes in in some way, probably more than that even thanks to how simple many of the mods are. The Digitama Hatchery server itself has over 12,000 members, so there’s potentially a sizable chunk of those that have experimented.”

All this is to say that those coming to Digimon nowadays have plenty of paths they can choose when it comes to taking that next step and getting into V-Pet modding.

This wasn’t always the case. For a long time, getting access to the inner workings of Bandai’s Digimon V-Pets remained something of a black box.



A member of the V-Pet community who goes by the name BladeSabre came up with the workaround that changed all this.

“I was playing around with Digimon prong signals and trying to build things on and off since about 2005 and finally published an Arduino project in 2014. I never guessed what the community would do with it,” BladeSabre said.

As part of a project later dubbed DMComm, she created a custom Arduino circuit that was able to mimic the protocols that Digimon virtual pets used to send information to one another.

By sending information to the serial port that the Arduino circuit was connected to, fans were finally able to speak the same language as the device that had captured their attention for decades.

BluDragon has a more colourful way of describing the significance of this breakthrough moment for those lurking in the Digimon Underground.

“It was freaking insane! It was genius!”
The D-Com devices built using this blueprint were essentially “the equivalent of a GameShark for a Game Boy game” and once you understood how to read the signals that virtual pets send to one another, you also understood how to manipulate them.
“You could cheese battles, you could spawn items for yourself through trading systems, you could create jogress partners out of thin air. It completely solved the problem of needing to battle to get to the higher stages but having no way to battle if you didn’t have someone else there,” BluDragon said.

According to Humulos, BladeSabre’s work “basically revolutionized a lot of what we understand about Digimon by creating an external piece of hardware that could intercept connection signals from the prongs on the top of Digimon devices.”

These days, external hardware based on BladeSabre’s original work is “super appealing” because it makes it easier to unlock content on the device and battle online with devices in a way that Bandai Namco never intended.

Of course, that last part didn’t happen overnight either.

Taking the battles that made Digimon different from other virtual pets online was its own problem. Fortunately, the idea for how to approach the problem came from one of the community’s younger fans.

Aged just 22, BluDragon was too young to experience the early 2000s highs of the Digimon franchise. Shortly after acquiring her first virtual pets, she found her way into the underground of V-pet modding.

That eventually led her to the moderator of a V-Pet forum called WithTheWill in search of an answer to a question.

‘Would it be possible to take the DMComm system online?’

The mod in question— BladeSabre— quickly provided an answer: No.

During battles, both virtual pets require information to move back and forth with a velocity that even the modern internet couldn’t support. Fortunately, rather than extinguish her ambitions outright, this explanation later nudged BluDragon in the right direction.

What if instead of creating a direct link between two V-Pets looking to brawl, there was a way to fake that connection instead?

“When two V-pets fight, they respond to each other packet by packet. One side will determine a winner or if the combination is good and the other side will double check that information and usually observe it as true.”
“As such, you get one side that wins and one that loses. In most devices, the initiating device is the one that does the majority of the maths while the other just confirms it,” BladeSabre explained.
“If we could make it so that the virtual pet decided the outcome instead of the Arduino then we could send codes to one another that are the battle data of the Digimon we raised.”

It was an ambitious idea, especially for someone with no programming experience. Fortunately, BluDragon found herself a mentor in the form of the same mod who had initially told her that online battles wouldn’t be possible.

In retrospect, she described her experience working and learning from BladeSabre as “fantastic.”

“To this day, I still have the skills of understanding binary and hexadecimal numbers and how to stare intently at that kind of information for a Digimon Virtual pet and determine what it is saying.”

“To this day, I still have the skills of understanding binary and hexadecimal numbers and how to stare intently at that kind of information for a Digimon Virtual pet and determine what it is saying.”

In the years since the two pooled their talents, both BluDragon and BladeSabre have gone on to become involved in what some consider the most ambitious project the Digimon Underground has ever undertaken

start W0RLD.exe
A Whole New W0RLD

The Digimon modding project to end all other Digimon modding projects.

W0RLD is a fan-made MMORPG that allows Virtual Pet owners to take their monsters online and explore a Pokemon-style overworld map while battling and training with other players. It supports over 20 different V-Pets and allows you to carry your progress from W0RLD back into your main game and vice-versa.

Under the hood, it’s an extension of the copy-based system that BluDragon and BladeSabre engineered.

“It’s basically the type of thing we wish Bandai would make,” Humulos said.

In contrast to BluDragon, Seki — the figure responsible for building the bulk of W0RLD — did grow up with Digimon back in the 90s. As an adult, he decided to pick up a modern V-Pet on a whim. Before long, he found himself asking the same question as Digimon fans before him.

Was there any way to play online? This inevitable question led him to BladeSabre and BluDragon’s fix. Rather than the end of the road though, this would prove to be the start of a journey to something even bigger for the V-Pet community.

As a long-time fan of MMORPGs, Seki saw how this workaround could be the foundation upon which an online V-Pet experience could be built. Better yet, with a background in game development, he actually had a lot of the skills and know-how needed to make that idea a reality.

At this point in his career, Seki already had worked on two other online titles: Pixel Tactics Online and BattleCon Online. The backend tech powering both these games provided plenty of shortcuts when it came to taking W0RLD online.

“It’s the little engine that could,” he said.
Digimon W0rld

Up until recently, Seki was the main programmer of W0RLD. Recently though, he’s handed over most of the day-to-day work to a small team of around seven other developers.

“Without these guys, W0RLD would be nothing,” he said.

While the difficulties of balancing his day job as a teacher with his role as the steward of W0RLD are part of the reason why Seki has stepped back, his desire to see the project continue without him is the other big reason.

“I wanted to make sure if something had happened to me the world would not miss W0RLD,” he said.

He adds that the project would never have survived as long as it has without the support of a Singapore-based V-Pet retailer named Zenin.

“Zenin is a BIG part that W0RLD even made it this far,” he said.

A few years back, Seki approached the company with a request for money to help build out a particularly ambitious feature for the game. Zenin agreed to help, and the site still sponsors the project today.

Where the kids of the 90s could only dream of taking their virtual pet online, those picking up a V-Pet now can do it with ease. Projects like W0RLD and DMComm add unprecedented depth that the baseline V-Pet experience just doesn’t have by default.

The hundreds of hours that Digimon fans have put in over the years have had a transformative effect on the relatively simple hardware it's built around. However, as the community around that hobby has grown in size, it has also faced challenges around how it deals with topics like cheating and piracy.

The line between an ethical or unethical V-Pet mod is a blurry one and this has put many of those who work to moderate that community in a weird position.

Digimon Battlin
Source: Bandai Namco Television Commercial for Digimon

According to Humulos, the need for etiquette “has only arisen recently, as most mods can’t really do enough to have serious negative impacts.”

“That being said, cheating when it came to online battling was a concern, as it’s very easy to modify the code being sent by the device after it reaches your computer and before you send it to your opponent.”

He said that he held off releasing the full documentation on how code signals worked until they had a way of dealing with this in place. For the most part, the Digimon modding community sees itself as sharing territory with that of the wider video game emulation world.

BladeSabre said that there's still some trade-off between information sharing and cheat prevention.

“Most of my work on the project has been open-source, which allowed others to build on top of it freely, but also makes things easier for people who want to cheat,” she said.

According to BluDragon, keeping piracy to a minimum is in both their best interests and those of Bandai Namco.

Humulos said that his community is very careful not to provide guidance on the hardware that enables one to extract and write images.

“We also don’t want to promote mods that would provide an unfair advantage by allowing directly increasing stats on the Vital Bracelet BE or removing intended timers.”

The Vital Bracelet V-Pet is an odd case because it is in some ways the most mod-friendly V-Pet Bandai Namco has ever released.

Pictured: 25th Anniversary Vital Bracelet BE (Digimon Fitness Bracelet)

From the perspective of some fans, the company hasn’t exactly been the best steward of the franchise over the last twenty years. Prior to the Vital Bracelet, Digimon fans got a single model with a colour screen whereas Tamagotchi players got dozens. That reluctance to offer hardware improvement to fans who would happily pay the premium has made it easier for the likes of BluDragon to make the device their own, but it also has its downsides.

The Vital Bracelet V-Pet was a complete departure from the expectations set by this status quo.

A hybrid of a traditional Digimon V-Pet, and a fitness watch, the Vital Bracelet represented something of a quantum leap in ambition over prior devices. For the first time, feeding your Digimon was replaced with reading biometric data. More than that, The Vital Bracelet was also the first Digimon V-Pet with online battles and a modular flash memory system.

For decades, fans have been adding their favourite or alternative Digimon where Bandai wouldn’t. Now, monsters could be stored and saved to a proprietary memory standard called DIM. The Vital Bracelet even supported firmware updates that could add new features and quality-of-life improvements, some of which were directly inspired by the work of modders.

As BluDragon puts it, this felt like a challenge to the modding community and a demonstration of just how much you could do with this particular device more than others. She feels like the firmware support here is less there for the company’s ends and more of a way to make it their own.

Despite that, there was some hesitation about modding the Vital Bracelet.

“This was our first time getting colour screens, changing rosters, all of that. So our response was that we cannot risk piracy hitting this in any meaningful capacity because if it does it could kill it and we will never have it this good again.”
“This put the modding community in a strange position because before any time we found something we would release that information whereas now we had to be more careful with that,” BluDragon explained.

While modding activity around the modern V-Pet bracelet has been relatively subdued to date, BluDragon believes there is a path forward where they could achieve a kind of mutually beneficial relationship with Bandai Namco that’s similar to the one that W0RLD has managed to carve out for itself.

“Bandai will gladly turn a blind eye to anything that Digimon does in general,” she said.

“At worst, it has no impact and at best it boosts sales.”

Perhaps that’s a little cynical. The community around V-Pets and how to mod them doesn’t exist in the way that a corporation does and sales are far from the only outcome that matters. The work of people like BladeSabre, BluDragon, Seki and Humulos adds up to something altogether different but no less valuable to those seeking it out.

Theirs is the house that hackers built. Bandai might have given them the bricks but they laid the foundations. Piece by piece, they’ve made this world a little more like the one they’ve imagined for decades.

Welcome to the Digimon Underground...
Fergus Halliday
Written by
Fergus Halliday
Fergus Halliday is a journalist and editor for Reviews.org. He’s written about technology, telecommunications, gaming and more for over a decade. He got his start writing in high school and began his full-time career as the Editor of PC World Australia. Fergus has made the MCV 30 Under 30 list, been a finalist for seven categories at the IT Journalism Awards and won Most Controversial Writer at the 2022 Consensus Awards. He has been published in Gizmodo, Kotaku, GamesHub, Press Start, Screen Rant, Superjump, Nestegg and more.

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