Japanese police have arrested three people over "sushi terror": viral, unhygienic pranks that are threatening the world-famous feature of sushi conveyor belt restaurants. Last month, a video of a man licking a soy sauce bottle on a sushi train went viral, sparking outrage. In the video, he can be seen rubbing saliva on passing dishes at a Kura Sushi restaurant branch. Since then, dozens of such videos have proliferated sparking public concern. Several sushi train restaurants - known as Kaiten-sushi in Japan - have made public appeals for offenders to stop their food sabotage. But some eateries have even made the choice to stop operating their main attraction altogether - with sushi conveyor belts coming to a halt across the country. In eastern Japan, the Choushimaru chain said it would stop using its conveyor belts altogether after a customer placed a cigarette butt in a jar of pickled ginger. Staff will now bring dishes to customers directly - and only hand out condiments and sauces when they"ve taken their seats. Japan is renowned for its exacting cleanliness standards and culinary etiquette. So the "sushi terrorism" pranks have not only shocked millions around the country but also led to falls in share prices of companies like the Sushiro chain. A spokesman for the Kura Sushi - the restaurant chain targeted by those arrested on Wednesday - said the viral video trend was "extremely dangerous" and posing a threat to the foundation of the conveyor-belt restaurant model. "Conveyor belt sushi is something we are proud of as part of Japanese culture. We want to make sure our customers can eat sushi delivered on the belt safely and comfortably," he said. People have filmed themselves licking presented chopsticks or touching sushi as it glides past them on the belt. One video which emerged last month showed a customer putting wasabi on someone else"s food order as it passed him on the belt. Several sushi chains have already threatened legal action - but Wednesday"s detentions are believed to be the first arrests of offenders. Police in the central Japanese city of Nagoya allege Ryoga Yoshino, 21, licked a communal soy sauce bottle at a Kura Sushi conveyor-belt sushi restaurant on 3 February. Two minors aged 19 and 15 were also involved. Police said their actions constituted obstruction of business under Japan"s Penal Code. All of the suspects admitted to the wrongdoing, police said. One also reportedly apologized for his actions. Restaurant-owning companies had already been struggling - with global supply chains under strain to a weaker yen, the war in Ukraine and the coronavirus pandemic. Many had to raise prices on their cheapest offerings last year. Now they face another struggle with the wave of unhygienic pranks. It"s led to restaurants around the country scrambling to reassure customers of their hygiene standards. The Sushiro chain changed its service rules last month, requiring diners to collect their own utensils and condiments from staff to cut down on potential sabotage attempts. Kura Sushi has now also developed an alert system, where some of its conveyor belts will now be equipped with sensors and cameras. If a person is caught returning a plate that has been tampered with, an alert will be sent to the chain"s offices in Saitama prefecture, near Tokyo and Osaka. The affected restaurant would also be informed, Kura Sushi said. The company said the new sensors would also be able to identify the specific plate and seat number affected. — BBC