Kazuki Takahashi is dead. He was just 60.

The author of the Yu-Gi-Oh! manga series that produced an extremely famous collectable card game, as well as various anime and video game spin-offs, was discovered dead this week in the Okinawa Prefecture of Japan, according to Thursday reports from NHK and The Japan Times. The author, whose given name was Kazuo Takahashi and who wrote behind a pen name, was sixty years old. 

According to NHK, authorities have not disclosed a cause of death and are currently investigating. On Wednesday, Takahashi's body was apparently discovered off the coast; he was supposedly traveling alone on a snorkeling expedition. 

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Yu-Gi-Oh! was first published as a manga in the Weekly Shonen Jump magazine between September 1996 and March 2004. Yu-Gi-Oh! revolved around the spiky-haired protagonist Yugi Muto, who, after completing an ancient artifact called as the Millennium Puzzle, summoned a mysterious spirit that powers his alter ego, Yami Yugi.

Together, they sought the ability to become formidable duelists in the ancient and futuristically modern game of Duel Monsters, and challenged others to high-stakes bouts. 

Multiple anime series, spin-offs, and animated films were later based on the Yu-Gi-Oh! manga. 

In 1999, the Yu-Gi-Oh! Trading Card Game debuted in Japan, and in 2002, publisher Konami brought it to the West. Over 35 billion cards have been sold since the game's inception. The anime and manga series were adapted by Konami into video games, with early versions for the original PlayStation and Game Boy Advance. In January, Konami released the free-to-play Windows PC game Yu-Gi-Oh! Master Duel, which became an unexpected hit on Steam. 

Before his death, Takahashi was still actively writing comics. In June, Marvel and Viz Media released Takahashi's Secret Reverse, a comic featuring Iron Man and Spider-Man in which Tony Stark flew to Japan to attend a gaming convention, where he met the CEO of a card game firm with ominous intentions.

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