YEAR after year, as Yoshiro Haga’s wealth and fame increased, his old friend and mentor, Toshio Kawashima, could only look on in jealous fury.

Mr Haga’s business grew and expanded while his friend sweated unrecognised in his single shop. His face appeared on television and in magazines, while the older man laboured in obscurity. Yet the secret formula on which Mr Haga’s success was based had been given to him by Mr Kawashima. Finally the sense of resentment became too much.

One night, Mr Kawashima and a colleague picked up Mr Haga, tied him up, put a bag over his head, and drove him around for six hours beating him up, to teach him what happens to those who steal secrets. Yet this dispute was not about industrial chemicals or a cure for cancer, it was over a recipe for Japanese noodles.

On Tuesday, Tokyo police arrested Mr Kawashima for the kidnap and assault of the man acknowledged as the creator of some of Japan’s finest ramen, or noodle soup. Mr Kawashima is said to have told police: “I taught him everything he knows about making a good soup and running a business, but he never greeted or thanked me. So I thought I’d make him taste a bit of pain.”

The case has been widely reported in Japan, demonstrating the passionate regard with which the humble noodle is held. There are 80,000 ramen shops in Japan, with sales of 800 billion yen (£4 billion) a year, at about 650 yen (£3.25) a bowl. The best among them — such as Aoba, the chain run by Mr Haga — are as celebrated and esteemed as the finest French wine producers.

Ramen reviewers rate the shops for consistency of the noodle, aroma and, above all, the taste of the piping-hot soup stock in which they are served. And it was over this that Mr Kawashima’s anger originated.

By his account, he had teamed up with Mr Haga 15 years ago and shared with him his recipe for stock on the understanding that the two would go into business together. Then Mr Kawashima fell ill, and Mr Haga set up on his own. The shop, Aoba, quickly became a success. Most authoritative ramen critics rate it in their all-time top five, and the single Tokyo outlet eventually grew into a chain of 12.

Mr Kawashima, 57, set up his own shop, Akibaya, which achieved no such acclaim. “I taught him my recipe and management know-how, but he’s been acting as if everything was his idea in magazine interviews and so on,” he said after his arrest. “I haven’t received a word of thanks or apology.”

The key to Aoba’s success lies in the innovation known as “double soup”. Rather than a single stock, Aoba’s chefs prepare two — a rich-tasting one made from pork bones and a plainer one made from fish and kelp. The two are united in the bowl just before the noodles are added to produce a flavour that delights ramen enthusiasts but which also has a broad appeal. “The soup is perfectly balanced,” Hirosaki Osaki, a ramen expert said.

Mr Kawashima’s ramen, by contrast, is “good for ramen fanatics, but not popular with the public,” according to Mr Osaki. “I don’t believe he was the one who taught Mr Haga the secret of the soup. The taste of Aoba ramen is not something that you can learn.”

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