A man was dismayed to discover a potentially valuable Pokémon card he had kept in mint condition for decades had been opened by his nephew.

In a post shared to Reddit, a user posting under the handle u/Simba_Rah, who asked not to be named, revealed how, upon returning home to his native Canada in sad circumstances, he realized his sibling's young son had found his pristine Pokémon card collection.

"I live in Beijing now with my family. My personal items were being stored at my childhood home. This includes my collection of original Pokémon cards from the nineties," he told Newsweek. "I had gone home for my father's funeral and was looking through my collection, and noticed that I was missing one of my cards. He actually took it and put it in his collection."

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The newly opened Pokemon card. The unnamed collector was surprised to come across the card. The newly opened Pokemon card. The unnamed collector was surprised to come across the card. Reddit/u/Simba_Rah

A popular favorite among kids and adults alike, the Pokémon franchise, set around the concept of a world where humans collect and train fantastical creatures to compete against each other in battles, dates back to the mid-1990s.

While much of the franchise focuses on a variety of video games and animated movies and television series, arguably the most enduring element has been the Pokémon trading cards, which have been known to fetch thousands of dollars among collectors.

In 2019, a mint condition set of Pokémon cards sold for more than $100,000 at auction. Those who have kept hold of their cards have also been encouraged to do so by stories like that of JC Smith, an avid collector who discovered his card collection was worth around $15,000.

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With cards continuing to fetch thousands on auction sites like eBay, the owner of the u/Simba_Rah Reddit account thought it best to take a look at his own collection.

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"As a child I knew the importance of keeping collector cards in mint condition," he said. "That's pretty darn hard to do. Kids want to open these things and touch them."

That's what made his nephew's act of mild-thievery that bit more frustrating. The card he opened, an "Ancient Mew" card, wasn't the rarest, per se, but the fact it was in mint condition made it more valuable than most.

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"They were mass produced for the launch of the Pokémon 2000 movie. It is a promotional card intended to be collected and not played with," he said. "This one in particular is of high quality and graded could go for about $300."

He said that when he first noticed the card was missing, he was surprised. Even more so when he realized his nephew had it.

"This collection was stored in my childhood room, in a binder, in a sealed plastic container so finding was absolutely a chore," he said. "But he had time, and I wasn't around. I also didn't know he was going around looking for these cards."

He said he had "no intention" of ever opening the Ancient Mew card, which dates back to 1999, and was "pretty annoyed" when he discovered what his nephew had done but, at the same time, didn't want to make too much of a big deal.

"The uncle-nephew relationship is a sacred one that shouldn't be trifled with," he said. "I talked to him about it, joked with him, and got him to understand the importance of these cards to me. I intend to give them to my own son when he's old enough and if he's interested."

However, he's also relieved his nephew didn't start playing around with some of the other cards in his collection. "The real treasure is stored in a particular binder housing two complete sets of the original release of Pokémon cards and my sealed Ancient Mew card," he said.

"When my nephew who collects Pokémon cards heard of these cards, of course he's going to want to see them. After all, I'm in possession of two shadowless Charizard cards, which is one of the most valuable cards printed."

He's now planning on sending the newly-opened card off to be graded along with a few other cards. Most will stay as part of his collection though, provided his nephew can keep his hands off them. "I'll have to keep an eye on him as often as I can spare," he said.

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