A game that reached millions under a stolen name. Underneath the theft was something genuinely worth finding.
Keitai Denjuu Telefang was released in Japan on November 3, 2000 — a monster-collecting RPG where the core mechanic was exchanging phone numbers with creatures and calling them into battle on a fictional cell phone called the D-Shot. It was a small, well-designed game built for a specific cultural moment: Japan in the year 2000, saturated with keitai culture, everyone newly carrying a device that changed how you reached people. The game never left Japan. Then Chinese bootleggers renamed it 'Pokémon Diamond' and 'Pokémon Jade,' printed fake cartridges, and sent it to street markets across Asia and ROM sites across the internet. The translation went Japanese to Chinese to English, producing dialogue so garbled that Denjuu received names like 'Hat,' 'Ice Cream,' and 'Game Boy.' The box art showed creatures that don't exist in the game, one borrowed from a Studio Ghibli film. Millions of people played it thinking they had obtained something rare and official. Many were confused. Some were delighted by the strangeness. A few went looking for the real thing underneath — and found Telefang. That discovery built a fan community that spent sixteen years translating the game properly, completing the work in 2024. The game reached its audience the wrong way, through the wrong name, via the wrong people. It arrived anyway.
About this game
Keitai Denjuu Telefang is a monster-collecting RPG released on Game Boy Color in Japan on November 3, 2000, in two simultaneous versions — Power Version and Speed Version. Players wield a device called the D-Shot, a fictional cell phone, to call sentient creatures called Denjuu into battle. The game was designed around the mobile phone culture of late-1990s Japan, with signal strength and phone book mechanics central to combat. It remained a Japan-only release throughout its commercial life. It is best known outside Japan not for its genuine qualities but for an accident of history: Chinese bootleggers sold hacked, poorly translated versions of the game under the titles 'Pokémon Diamond' and 'Pokémon Jade,' distributing them globally as counterfeit Nintendo products. Millions of people encountered Telefang without knowing it.
The Story Behind
Smilesoft, a small Tokyo publisher founded around 2000 and headquartered in Shibuya, released Telefang as part of a short catalog entirely focused on monster-collecting games. The company closed in 2003 when its president was arrested on unrelated criminal charges. Its game licenses passed to Rocket Company, a successor entity operating from the same address with identical business details. Telefang's developer was Natsume, a separate studio known primarily for the Harvest Moon series. The bootleg version — sold on counterfeit cartridges as 'Pokémon Diamond' (Power Version) and 'Pokémon Jade' (Speed Version) — originated in China and spread through Asian street markets and international ROM-sharing websites by approximately early 2001, within months of the legitimate game's release. The names Diamond and Jade were chosen to align with the Pokémon Gold and Silver branding then current. When Nintendo released the actual Pokémon Diamond and Pearl in September 2006 (Japan) and April 2007 (North America) for the Nintendo DS, documentation pages on multiple wikis explicitly clarified that the GBC bootleg was not related. The real game's fan community, which grew around the bootleg's notoriety, spent sixteen years producing an official English translation patch, completed in 2024.
Tricks & Tales
The bootleg cartridges carried an accidental layer of irony: they included anti-piracy protection built by the counterfeiters themselves. The save system used custom hardware registers not present on licensed cartridges, meaning the bootleg games could not save progress on standard flashcarts or emulators — piracy-protecting their own piracy. The translation pipeline (Japanese to Chinese to English) produced famously absurd results: the creature 'Crypto' became 'Kuribute,' and other Denjuu were renamed 'Hat,' 'Ice Cream,' and 'Game Boy.' The box art of 'Pokémon Diamond' depicted a blue snake-like creature that appears nowhere in the actual game; 'Pokémon Jade' featured a modified version of the Forest Spirit from Studio Ghibli's Princess Mononoke. The creature designs for the real game were created by Saiko Takaki, a freelance illustrator known for Vampire Hunter D manga artwork. The soundtrack was composed by Kinuyo Yamashita — the composer of the original Castlevania (1986) — credited under her married name Kinuyo Ueda.
Collector's Guide
Region & Compatibility
Like the original DMG, the Game Boy Color is fully region-free. Japanese, North American, and European GBC cartridges all share the same physical format and connector, and the hardware applies no lockout. A Japanese GBC cartridge will run on any GBC from any region without modification. The GBC is also fully backward compatible with original DMG cartridges — when a DMG cart is played on a GBC, the system automatically renders it with one of several colour palettes. GBC-specific cartridges (the 'GBC only' black-tab type) will not run on the original DMG, but will run on the Game Boy Advance as well as the GBC.
Maintenance Tips
Game Boy Color cartridges — the smaller, slightly translucent-shell format — use the same cleaning approach as original DMG carts: a cotton swab with 90% or higher isopropyl alcohol wiped along the contact row, allowed to dry fully before reinsertion. The GBC console's ABS plastic shell faces the same yellowing risk as the DMG when exposed to UV light over time. Notably, several GBC titles — most famously Pokémon Gold, Silver, and Crystal — include a real-time clock (RTC) circuit that runs continuously off a CR2025 coin cell. These batteries are now well over 25 years old; a dead RTC battery means time-based in-game events will not advance, even though the game itself will still load and save normally. This is a distinct issue from save data loss.
Going deeper
Explore the machine this game ran on, and what to check before you buy or care for one:
What to Watch Out For
Before buying, these are the points worth knowing — from someone who handles original Japanese Keitai Denjuu Telefang copies regularly.
How do I tell a genuine Japanese Telefang cartridge from a counterfeit 'Pokémon Diamond' or 'Pokémon Jade' bootleg?
Authentic Japanese Telefang cartridges bear the Nintendo licensing mark ('Nintendo GAME BOY' or 'Nintendo GAME BOY COLOR') on the cartridge label and use standard Nintendo gray or black plastic shells. Bootleg 'Pokémon Diamond' carts often appear in non-standard white shells, while 'Pokémon Jade' bootlegs frequently use translucent green or black shells. All bootlegs use a simplified screw type rather than Nintendo's proprietary 3.8mm security game bit. The label of a genuine Japanese Telefang cartridge reads '携帯電獣テレファング' and displays Smilesoft's publishing mark — it bears no Pokémon branding whatsoever. If the cartridge says 'GAME' or 'GAME COLOR' instead of 'Nintendo GAME BOY,' it is not a Nintendo-licensed product.
The 'Pokémon Diamond' I have won't save. Is it broken?
This is almost certainly a bootleg Telefang cartridge, and the save failure is intentional, not a defect. Chinese bootleggers built custom hardware registers into the cartridge to implement their own save system, which only functions on that specific non-standard hardware. On genuine flashcarts, emulators, or standard MBC hardware the save code either freezes or resets — a side effect of the counterfeiters having copy-protected their own counterfeit product. The original legitimate Telefang game saves normally.
Is an original Japanese Telefang cartridge region-free? Will it work on a Western Game Boy Color?
Yes. The Game Boy Color has no hardware region lock. A Japanese Telefang cartridge plays on any Game Boy Color or Game Boy Advance console worldwide without modification. The game is in Japanese; no official English version was ever released commercially. A fan-produced English translation patch was completed in 2024 and can be applied to a ROM dump of the original cartridge for play on an emulator or flashcart.
Is the bootleg 'Pokémon Diamond' GBC cartridge itself a collectible?
Yes, with important caveats. Boxed examples of the bootleg Pokémon Diamond and Jade cartridges have sold for approximately ¥15,000–¥18,000 (around $125 USD) at peak — notably more than a legitimate Pokémon Crystal at the time — driven by their historical notoriety and the absurdity of the mistranslation. However, they are not Nintendo-licensed products and have no connection to the official Pokémon Diamond and Pearl (DS, 2006). If you are specifically looking for the authentic Japanese Telefang experience, seek the original Smilesoft-published cartridge, not the bootleg.
Before You Buy
Things worth knowing before you buy Keitai Denjuu Telefang
A short checklist for buying a used Game Boy Color cartridge wisely — useful with any seller, anywhere.
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Choose a seller who tests it before shipping
A copy that has actually been powered on and checked is a known quantity. An untested one is a gamble you only settle after it arrives.
Look for a seller who states it was function-tested and says what they confirmed. A serious seller can tell you exactly what was checked.
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Good news — Game Boy Color is region-free
These cartridges are not region-locked, so a Japanese copy plays on any compatible Game Boy worldwide.
Confirm whether the title is Color-only or also works on the original Game Boy.
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If this title saves your progress, check the battery
Cartridges that save use a small coin-cell battery that fades over decades — a dead one wipes your save without warning.
Ask the seller whether the save function was tested. Replacing the battery is possible, but doing so erases any existing save.
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Check that the contacts are clean
Dirty edge contacts are the most common cause of startup and sound trouble in cartridges of this age.
Choose a seller who cleans the contacts before shipping. A note that it was tested and cleaned means the basics were handled.
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Read the seller's reviews and return policy
A 100% positive record across thousands of sales is close to a guarantee — packing, communication and problem-solving all work for everyone. A return policy protects you if something is off.
Read the feedback and confirm a clear return window before you buy.
The last step before buying anywhere is knowing what it's worth.
See what it's selling for on eBay →Unexpected Discoveries
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