Ok. Enough. "Deliberately ensnared a foreign wife" ?!
There is nothing to suggest that MIL will be ashamed of her foreign daughter in law, my in laws weren't at ALL and they come from an extremely rural part of Japan, so rural in fact that I am the only white person they had ever met in person and they were int heir late 70s when I met them. They were absolutely lovely to me and even though we are separated I still am extremely fond of them both and consider them family.
For the umpteenth time, this is NOT about submission. It is about managing to adapt to a different culture in such a way that your life and your child's life will be comfortable. You move to Japan, marry into a Japanese family? Expect to have to fit in with Japanese values.
As I have previously stated, I cannot imagine that if someone from another culture tried to enforce their culture on a British family having moved to the UK, married a British man and were living in their mother in law's house that everyone would be jumping to their defence.
British culture is NOT superior to the rest of the world. It is just different. This "poor woman" is not, IMO, "trapped". She has to learn to compromise within a Japanese family, otherwise life will be a struggle. Just as it would be of the shoe was on the other foot, and don't pretend it wouldn't be, because it absolutely would. People in the UK insisting that you can't expect grandparents to help with childcare, for example. In many cultures the idea that grandparents are not heavily involved with the raising of children is completely alien. In Spain, for example, grandparents have visitation rights for their grandchildren, if the parents prevent them from seeing their grandchildren they can be taken to court.
This lady is going to have to fit in, or it's going to be difficult. When in Rome etc. Suggesting that she should totally disregard the culture she has chosen to immerse herself in is so counter productive to the future happiness of herself and her family.
The UK has multiple misogynist issues. The total lack of public childcare provision is one. The fact that fathers who don't pay maintenance face almost zero consequences is another. The appalling state of maternity care is another. In Japan, OP will not end up being bundled out of the hospital within hours of giving birth, for example. She will not be left to fend for herself with her baby, she will be properly supported.
There are issues in Japan. There are issues in the UK. Nowhere is perfect. But again, I see zero evidence that this lady is "trapped" or "abused". She is having a bit of an awkward moment with a minor culture clash with her MIL. She needs to learn how to navigate that in a diplomatic fashion for the good of herself and her family.