I believe that if everything is in your wife's name, meaning whatever purchases or debt she has, is in her name only, and you are not mentioned as a guarantor or anything, you don't have any liabilities, first of all.
I assume you got married according to the Japanese law? Then if the two of you agree, you should be able to divorce by agreement (reporting to the city hall).
There are papers people often draw up upon divorce to document their agreement, over the assets, children, etc. In your case it might be wise to draw one up that says that you will not be liable for any repayment of debt or for raising her children, and that you will not be the guardian for the children, etc., if she agrees to it.
But even without this written agreement, if you do divorce by "agreed divorce" and it is accepted at the city hall, then the former couple would not have any mutual support obligations at all, so the divorce should leave you with no finaicial or whatever obligation.
However, somehow if she manages to make divorce difficult (by not agreeing to divorce unless you pay, etc.) she could take it to court... but what can she claim? You are not at fault, so she cannot file for divorce due to: any circumstances on your part that makes it impossible to continue marriage, adultery, etc. So if she lacks causes for filing for divorce. She tries to sue you for... what damages have you done to her, none, right?
She might try to file at a court demanding money from you (for whatever, compensations for whatsoever). However, (it goes back to the first paragraph) she is not entitled to anything.
All she can do is to deny you the divorce and give you trouble. I don't think she can claim anything from you, but if she acts like she might try to, keep notes of every purchase/debt she incurred unreasonably, done unreasonably, everything you've paid for the family, so that you can present the facts in a credible way to the family court. Better consult a lawyer, of course, but the above is what I know. Best wishes.