Japanese Police Detains Yoshihiro Yamakawa For Pokémon Game Hack

A Japanese man was detained after he allegedly used a Pokémon game hack to create and sell unique monsters.

TakeAway Points:

  • Yoshihiro Yamakawa, is charged with breaking into Pokémon Scarlet and Violet, saving data illegally, and breaking a statute against industrial espionage in Japan.
  • According to the report, Yamakawa ran promotions on an online marketplace that sells game characters and content, offering discounts on uncommon and difficult-to-train monsters like “6 Pokémon for only $30.”
  • The 36-year-old  was taken into custody by the Kochi Prefectural Police on April 9th after cyber patrol agents discovered him selling the characters on the internet.

Pokémon’s Hack

Japanese authorities detained that individual after discovering proof of his illicit tampering with save data for the Nintendo Switch titles Pokémon Scarlet and Violet, which he used to build bespoke characters he sold on an internet gaming marketplace. 

According to machine translations of stories at NHK and the Asahi Shimbun, the Kochi Prefectural Police arrested 36-year-old Yoshihiro Yamakawa on April 9th after cyber patrol officers caught him selling the characters online. Yamakawa, who used an online tool to modify the game’s save data, was arrested under suspicion of violating a Japanese law known as the Unfair Competition Prevention Act.

The police report, according to both outlets, states that the Japanese police cyber patrol caught Yamakawa in the act of taking orders. Yamakawa offered deals for hard-to-train and rare monsters, such as “6 Pokémon for only $30,” on an online platform that sells game assets and characters.

As we noted in our review of the games in 2022, battling and collecting monsters is an unsurprisingly major focus, and both titles were jam-packed with new, never-before-seen monsters. Players go on increasingly difficult raids to capture exotic and hard-to-find monsters, with the goal of training, battling, and, in some cases, even breeding them. It turns out some players covet rare pokémon enough to buy them on the black market. 

Demand for Pokémon

There has been sufficient demand in the past for this to occur. In a case that appeared to be similar to this one, Japanese authorities detained a guy in 2021 for breaking the law by tampering with the save data of Pokémon Sword and Shield. The Pokémon Company started to tighten down on cheaters since hacking into the save data of Pokémon games became so common, as Polygon reported in its report on the incident.

Between December 2022 and March 2023, Yamakawa allegedly sold his custom monsters for up to 13,000 yen each, which is roughly the equivalent of $85. Although Yamakawa reportedly confessed to the charges, telling officers, “I did it to earn a living,” the case is still under investigation. Police suspect that Yamakawa’s total profit amounted to millions of yen (equivalent to anywhere between tens and hundreds of thousands of dollars), and an investigation is underway.


Pokémon is a series of video games that were created by Game Freak and released by Nintendo and The Pokémon Company, under the Pokémon media franchise. The first two games, Pocket Monsters Red and Green, were released in Japan in 1996 for the Game Boy. Later, they were released outside of Japan as Pokémon Red Version and Blue Version. Satoshi Tajiri created the series with help from Ken Sugimori. Each new generation of Nintendo handhelds has seen the continuation of the main RPG series, which their developers refer to as the “core series.” On November 18, 2022, Pokémon Scarlet and Violet, the most recent games in the core series, were released for the Nintendo Switch.

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