Three-hundred-day problem

The Three-hundred-day problem is the legal presumption that a child born within three hundred days of a divorce is the former husband’s child. The novel presents it not only as a rule governing parentage but as a point where family life and official records can diverge: when a birth goes unreported to avoid the presumption, a child may grow up outside the system that establishes legal identity and makes people legible to public institutions.

The rule and its consequences

The issue arises when a woman divorces and has a child with a new partner within the three-hundred-day period. Because the law attributes the child to the former husband, some women in this situation— including women who have left abusive marriages—may refrain from submitting a birth notification. The child can then enter society without a family register, despite meeting the conditions for Japanese citizenship.

The consequence is more than an unresolved question of parentage. Without registration, the state may not know that the child exists; if that person later dies, the death may likewise go uncounted. The novel describes this as an erasure that encompasses both arrival and departure: official records recognize neither event. In the context of people lost in the tsunami, that absence also complicates the accounting of victims. The rule thus links a decision made around a child’s birth to the possibility that the child will remain unseen in life and death.

Family registers and administrative visibility

The discussion broadens from the three-hundred-day rule to the history of Japan’s family register. The system began in the late sixth century under the Ritsuryo bureaucracy, initially serving purposes such as policing and taxation. In the Edo period it also helped authorities monitor religious affiliation and enforce controls on Christianity, while records came to include details such as birth, marriage, adoption, address, occupation, and death. Yet many people, including vagrants, remained outside the system.

The modern register followed the recognition of freedom of movement in the Meiji period, when a land-based system had become obsolete. The new records were used for conscription and taxation, purposes that led some people to abandon or falsify them. The conversation also notes that wartime destruction of government records left some people without registers when they failed to report that records had been lost. Later safeguards—local originals, copies held by Regional Affairs Bureaus, and digitization—made a repeat of that particular loss less likely, but did not resolve every route into administrative absence. Children whose births went unreported remained an example of people missing from the record for reasons the archive itself could not repair.

The register’s history therefore frames the Three-hundred-day problem as part of a larger tension: official records can secure recognition, but the state’s methods of classification have also served control and exclusion. Nakakita connects exclusion from the register to being left outside the nation’s recognized social body, and points to Japan’s assimilation policies on the Korean Peninsula as another expression of the power to determine whose identity is officially acknowledged.

The rule as a clue in the investigation

The issue becomes a possible lead in Kido’s effort to understand X’s identity and the apparent exchange involving Daisuké Taniguchi. Kido had been considering whether Daisuké was living under X’s identity. After hearing about unregistered people, he considers the reverse possibility: X might have been the person absent from the register, while Daisuké assumed a place in the records. If so, the state might fail to recognize Daisuké’s murder; a body could be treated as unidentified, and a death without physical evidence could be exceptionally difficult to establish.

This remains a hypothesis, not a finding. Kido also considers the possibility that the tsunami could have washed away physical evidence, compounding the problem of a person whose existence was not recorded. The rule’s narrative importance lies in the investigative question it opens: identity exchange is not only a matter of one person using another’s name, but may depend on who is present—or absent—in the administrative record.

The register in the novel’s legal world

Elsewhere, Kido’s work for Rié shows how a family register can be altered through court procedure. After X dies, the record treats him as Daisuké Taniguchi, even though he was not the real Daisuké. Kido petitions the Miyazaki Family Court to cancel the death-based removal of “Daisuké Taniguchi,” restoring him to the records as alive so that the police are no longer left with a missing-person report for someone officially dead. He then seeks to remove that identity from Rié’s register and restore her maiden name, Takemoto, annulling the marriage on the basis of error. The revisions erase the second marriage from the register and make Hana legally illegitimate.

That legal process is a distinct instance of the register’s power to define family status, not an application of the Three-hundred-day problem itself. Read together, the cases show how both a false entry and a missing entry can shape who the law recognizes as a spouse, a parent, or a person whose life and death can be counted. The novel’s concern is not simply that records may be inaccurate; it is that their categories and omissions have consequences in lived family relationships as well as in state administration.