The Spouse can receive the Greater of Y160M + the Basic Deduction, or the Spouse's Statutory Share of the Estate + the Spouse's share of the Basic Deduction completely free of Inheritance Tax, no matter how large the Spouse's Statutory Share of the Estate...
Thanks Ben and Tkydon! The conversion from Japanese numbers to English always gets me… Anyhow, the free inheritance allowance seems fine to me since the point of the inheritance tax is to keep wealth from becoming concentrated in a privileged class.