Osaka-based Akindo Sushiro filed the suit with the Osaka District Court, seeking damages of about 67 million yen, or about 480,000 dollars.
The video, taken at a Sushiro outlet in Japan's central city of Gifu, shows a diner licking the spout of a communal soy sauce bottle. He also licks his finger and touches a piece of sushi as it goes past on the conveyer-belt.
The company says the video led to a sharp drop in customers nationwide and caused the stock of the restaurant's parent company, Food & Live Companies, to slump. Akindo Sushiro argues it suffered a loss of about 115 million dollars as a result.
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Lawyer says prankster admits to the act, regrets his actions
The prankster's legal counsel in May submitted a written request to the court asking it to dismiss the complaint.
The document says the prankster admitted to the act and regrets his actions. It argues that the decline in customers could be attributed to fierce competition in the restaurant industry.
A lawyer representing the prankster declined to comment, citing a confidentiality obligation.
Eateries fight back against 'sushi terrorism'
Earlier this year, a number of unhygienic so-called "sushi terrorism" prank videos went viral after being posted online. The phenomenon is seen as a social problem in Japan.
Several of the clips triggered legal action by the companies targeted. But the restaurants' biggest challenge has been to restore customer confidence shaken by the pranks.
Historically, Japanese people have been drawn to conveyer-belt sushi eateries for their speed, variety and value. Customers enjoy a wide array of choices, and the unique service makes it popular with tourists.
But not anymore at some kaitenzushi restaurants. They have changed their business model in order to win back customers. At some restaurants, chefs are now making each dish to order instead of placing the sushi on the conveyer-belt that winds past diners.
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