Japanese ferment their soybeans when eaten as food - this fermentation chemically changes it.

However, I was referring to the soybean oil.

Soybean oil is not used in cooking inside the Japanese home, but used for fast food/restaurant cooking.

https://www.world-grain.com/articles/16740-soybean-oil-deman...

Next time you get virtually any salad dressing or even a non-sriracha hot sauce such as that served in little packets from e.g. Wendy's or McDonald's, you will find soybean oil as one of the ingredients.

Soybean oil is nearly impossible to avoid if you are eating out; and it is found in a lot of other foods such as salad dressing, etc. I would encourage you on your next trip to supermarket to make note of how many processed foods contain soybean oil. Only good quality olive oil is free from PUFAs among the various vegetable oils.

(edited for clarity)

The Japanese eat soy in more forms than nattō and soy sauce.

If your point was blaming soybean oil say that instead of a blanket statement that soy causes obesity.