>Every time I worked on Japanese cars I seem to always
>have the issue that Japanese bolts, nuts and screws are always made of
>soft metal. If you are not careful they got destroyed and their heads got
>rounded off.

They're made of different grades/heat-treatments of steel just as US
and European metric bolts are, and for the same reasons.  Working on
a number of Toyotas, one Subaru and one Honda, I've experienced
nothing different than when working on Vanagons, except that the
Toyota bolts are much more likely to unstick very suddenly and then
be immediately removable with the fingers, which points to some
advanced engineering in how the bolt head seals to what it's attached
to.  Once when I applied grade-8 tightening torque to a grade-4 bolt
on a Corolla, the head came off the bolt, but I can't blame that on Toyota.

Yours,
David