The men, all in their 40s and 50s, dined at a restaurant in western Wakayama city on Friday night, the city's health official said.
They were taken ill early the next day, experiencing breathing difficulties and vomiting, the official said.
"They consumed a dinner that included liver, which is regarded as toxic material," she told AFP, reading from a statement.
The city shut down the establishment for five days from Sunday, she said.
The restaurant served the banned, poisonous parts after requests from the diners, the official said.
The livers, ovaries and skin, among other parts, of the puffer fish -- also known as the blowfish or "fugu" in Japanese -- contain toxins powerful enough to kill an adult, in the worst case scenario.
Aficionados say the tingle that the organs leave on your lips -- caused by the potent neurotoxin they contain -- is part of the appeal.
Every year, several people in Japan are hospitalised after eating fugu.
In order to get a licence for serving the fish, restaurant chefs must train for years to pass a stringent exam, which includes paper and practical tests on how to distinguish poisonous parts from others.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
