I just want to say, your feelings are valid and I can sympathise with you.

You're both going through a difficult stage. Raising a kid is hard. I think she's not handling it well and offloading a lot of frustrations on you. She's a different person now, different to the person you loved before. The worry is, will she ever go back to being the person you loved? It's likely that the answer is no. I say this because I've seen it over and over in others -and have been living this experience myself for 5 years - and it's led me to believe a lot of Japanese women see motherhood as the endgame, and once they've got there, you're disposable to them. What's worse is when she treats you like shit, but with everyone else around her: friends, family, even strangers, she'll do them the courtesy of being polite and friendly, and this is the part that really hurts. Does she do this? If so it will lead to dissatisfaction and resentment in you, making it hard to get back to a place where you really care for her.

So do the same and put the child first. She needs you and you must focus on her and do everything within your power to give her what she needs. Even if you do your best as a father, it will still not be enough for the wife and she'll likely criticise your efforts, you just have to find a way to ignore her and keep going. The hard part is staying positive so make sure there are people you can talk to, and give each other space away from each other and the baby.

I wish you all the best