Can someone give me an informed opinion on the necessity of health
checks in Japan?

My understanding (based on something I read some time ago) is that it
was a legal requirement for companies to offer them to their staff,
but not a requirement for the staff to take them. Of course it could
be a company rule that they are taken, but I'm interested in the legal
position.

I've taken the pointless test in the past without complaining, but
this the dates all happen to be inconvenient for me, however the form
we were given claims that the law requires us to take the test. Plus,
in the last year I learnt that Japan has by far the highest rate for
cancer caused by excessive x-ray usage (2.9% of all cancers are
attributable to this cause, which means 7,500 cases, compared to 0.6%
in UK and 0.9% in the USA). I've already had more x-ray exposure in 3
years here than in the previous 30+ in the UK.

James