Recently, a netizen posted on Threads about a cultural creative product that is both “fascinating and frightening”: a “marine mammal stomach worm ballpoint pen” from Kochi, Japan, which actually contains live crawling parasites sealed inside the pen’s barrel, stirring widespread discussion.
The netizen explained that this unique pen originates from Kochi Prefecture in Japan, an area famous for its bonito fish, but also notorious for parasites commonly found inside these fish. A local fish vendor came up with the idea of placing worms picked from the fish intestines into a transparent pen barrel to make a product.
According to the shared information, each pen contains about 30 worms, and when freshly assembled, the worms can even still be seen wriggling, with a lifespan of about 2 to 3 weeks. The business owner added that production volume depends on the daily fishing situation—“more fish means more worms,” making it possible to mass produce; otherwise, there might be no product available for the whole week.
The post also mentioned that this creative attempt started simply as something “fun” for the seller, inspired by seeing someone collect surgically removed parasites inside a pen. Surprisingly, after launching, the product went unexpectedly viral and has even become a specialty item. There’s also a local saying that older generations believe eating bonito sashimi is safe “as long as you chew well” to deal with the parasites. However, this kind of belief is generally considered lacking in scientific basis. The original poster jokingly remarked that if anyone does end up hospitalized due to eating raw fish, “maybe they can use this pen to sign paperwork,” adding further fuel to the discussion.
After the news broke, netizen reactions were divided. Some exclaimed: “Even through plastic, it still gives me goosebumps.”
Others joked that this would be the ultimate “landmine gift” in a Christmas gift exchange, while some thought it was incredibly creative and said, “I’d want to buy one as a collectible.”
There were also netizens with medical backgrounds who reminded people that while these parasites won’t grow inside humans, they can still cause severe abdominal pain and other symptoms. Some even shared personal experiences of friends and family needing medical attention after accidental ingestion, sparking further debate over food safety. As for whether such items can be brought through customs, some were curious, but most people guessed they probably wouldn’t pass quarantine regulations.