Hmm, don't know about the Japanese version but in my PAL version I can change it in "Driving 1" in options.
Ok so Main Menu -> Options (last one) -> Driving 1 (3rd one) -> Steering Wheel Force Feedback (4th one). It should be set to Medium by default. There's only 3 settings, Low, Medium and High.
Hope that helps.
By the way, why do you have a Japanese version if you can't really read Japanese?