After incidents of “sushi terrorist” were reported online, shares in Japan’s most famous sushi restaurants plummeted.

Social media has seen a number of videos showing customers tampering with food at some of Japan ‘s conveyor belt sushi restaurants (known as kaitenzushi), sparking outrage.

One of the most popular videos, which has been viewed over 40 million times, shows a young male licking the top of a common soy sauce bottle. He then places the teacup rim on top of a stack of clean cups.

In the 48 second video, he continues to lick his fingers and touch two pieces sushi.

Others videos show people adding wasabi to sushi of other customers and using a spoon to eat green tea powder.

The Guardian reported that while the parents of the criminal chef in the video have apologised to each other, stock prices in the Sushiro chain, where the video was shot, plummeted by almost 5% on Tuesday.

According to the company, it plans to pursue criminal and civil proceedings.

Hama Sushi and Kura Sushi also stated they plan to sue and will place cameras on conveyor belts in order to monitor diners.

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Sushiro stated that it has cleaned all its soy sauce cups and replaced all of the bottles. Customers are asked to collect condiments, utensils at a point of service rather than placing them on individual tables.

Japan is a country that has high standards of hygiene and where the sushi industry is valued at PS4.7bn, so videos of “sushi terrorist” have been viewed with outrage.