A transgender man has filed a lawsuit in Tokyo seeking legal recognition as the father of a child conceived using an egg retrieved from him prior to his legal gender change. The case raises complex questions about Japan’s parentage laws and their treatment of transgender families amid evolving medical and social realities.
The man, in his 40s and living in Tokyo, had eggs collected while he was still legally registered as female. One of those eggs was fertilized with donor sperm through in vitro fertilization (IVF) and implanted in his female partner, who gave birth to the child in November 2024. The man legally changed his gender to male the following month, and the couple married in February 2025. They then sought to have the man officially recognized as the child’s father by submitting a paternity acknowledgment form to a Tokyo ward office. However, the application was rejected, with authorities citing existing legal frameworks that define fatherhood primarily through a biological connection to sperm.
Under Japan’s Civil Code, the legal mother is generally the woman who gives birth, while a child born to a married woman is presumed to have her husband as the father, even if he is transgender and not genetically related to the child. This presumption does not apply retroactively if the child is born before the parent’s gender change and marriage, as in this case, leaving no legally recognized parent-child relationship between the man and the child despite their genetic link.
The lawsuit, filed with Tokyo Family Court last week and with the child listed as the plaintiff represented by the mother, challenges these legal interpretations. The family’s attorney, Shun Nakaoka, emphasized that assisted reproductive technologies and gender transitions are becoming more common and that the courts are lagging behind these developments. At a press conference, Nakaoka argued for recognition of the man’s biological fatherhood and the parent-child relationship based not only on genetics but also on shared life and emotional bonds. “We want to have a society where sexual minorities can have families as a matter of course,” Nakaoka said.
This case follows a June 2024 Supreme Court ruling, which recognized a transgender woman as the legal father of a child conceived with her sperm, despite her legal gender being female at the time of birth. The court had noted that Japan’s Civil Code does not explicitly require a legal father to be male and stressed that parent-child relationships should prioritize the child’s welfare, including rights to support and inheritance.
In contrast, the current case presents the inverse scenario: whether a transgender man, legally recognized as male but genetically connected through an egg rather than sperm, can be acknowledged as the child’s father. The suit highlights gaps in Japan’s family law, which was largely developed before modern assisted reproductive technologies and legal gender changes, leaving many nonheterosexual and transgender families without clear legal protections.
Legal experts and advocates alike note that the case poses broader questions about how Japan’s legal system can adapt to contemporary family structures. As Nakaoka stated, recognition should be based on the realities of family life rather than outdated legal definitions. The Tokyo Family Court’s decision is anticipated to have significant implications for transgender parental rights and the interpretation of family law in Japan.