A bizarre Japanese novelty product known as the “sea animal stomach worm pen” has gone viral again, sparking global fascination and disgust online due to its unusual and unsettling design.
Originally introduced in 2021 by Japanese seafood company Tada Suisan, the pen—also known as the Anisakis ballpoint pen—contains live parasitic worms suspended inside a transparent ink tube filled with preservative oil.
The worms, known as Anisakis or “sea stomach worms,” are commonly found in marine fish. In this product, around 30 live worms are sealed inside each pen, where they can be seen twisting and moving as the pen is shaken or used. The creatures reportedly survive for up to two to three weeks inside the sealed environment before eventually dying and remaining preserved inside.
The company behind the product said the idea originated from fish-processing waste, as the worms are routinely removed from caught fish. Instead of discarding them, the team experimented with placing them into pens as a form of “creative reuse,” which unexpectedly turned into a viral sensation and sold out quickly upon release.
The pen is priced at around 950–1,100 yen (approximately RM30–RM40 / HK$50–$60), but availability is highly unpredictable, depending entirely on how many infected fish are processed on any given day. On some days, dozens can be produced; on others, none are available at all.
The product has resurfaced on social media platforms such as X and Threads, where it has once again divided opinion. Some users joked it would make the “ultimate prank gift” or a nightmare office present, while others expressed discomfort, calling it “too creepy to even look at.”
Beyond the shock factor, the product has also drawn attention for its unusual biological preservation setup. The worms survive in a special plant-based preservation oil, which creates a low-oxygen environment similar to their natural habitat inside fish. The thick liquid also slows their movement, creating the visible “floating and writhing” effect inside the pen.
Engineers have also pointed out that the pen requires careful sealing technology to prevent leakage, as both oil and organic matter must be securely contained under airtight conditions.
While novelty items like this continue to gain attention online, experts also remind the public that Anisakis parasites can cause serious stomach illness if accidentally consumed in raw or undercooked seafood, although proper freezing and food handling in Japan generally prevents such infections.
Despite its unsettling concept, the “parasite pen” has become a cult internet item once again—blending biology, engineering, and shock marketing into one of Japan’s most controversial souvenirs.
