If you are an average person with average assets, you shouldn't be thinking about doing anything drastic or risky or complicated to avoid one or the other spouse from paying inheritance tax. In Japan, the spouse gets the special benefit of a 160,000,000 tax exemption on inheritance (as mentioned in the Reddit article).
You shouldn't be considering transferring assets unless your assets are well over 100 million yen. Also, the value of the real estate will be based on the assessed value for fixed asset tax (real estate tax). This value is far less than what you paid for the real estate, so even if you paid 100 million yen for the house, the tax-assessed value would probably be less than 50,000,000 yen. It sounds like you've already bought a house, so you will know the assessed value because it shows on the real estate tax bill you get every year from your city/ward.
In short, don't worry. If you are young, its better to worry about life insurance. If you are old, and your house is less than 160,000,000 in assessed value, you shouldn't worry about anything at all except for your wife's ability to take care of herself after you are gone (probably a mix of insurance, investments, cash, and nenkin).
If you have kids, the above calculations all change, but in most cases the inheritance tax rules become even more generous.