At the time of A and B’s birth, Paraguayan law allowed the mother’s passport to provide the children’s identity information along with their photographs. The mother and the children were able to leave Japan using this passport and return to Paraguay. However, the practice of providing children’s information on the mother’s passport was abolished at the end of March 2015. As a result, the identity information of the children was no longer shown on the mother’s passport, and it became impossible for the children to travel abroad using the mother’s passport. The Constitution of Japan adopts the jus sanguinis principle. As both of the parents of A and B have Paraguayan nationality, Article 2(iii) of the Japanese Nationality Act, which provides for acquisition of Japanese nationality by birth, does not apply to A and B. Therefore, A and B are stateless persons, as they did not acquire the nationality of any State by birth, and they are not considered as a national by any State. (3) Acquisition of nationality If A and B live permanently in Paraguay and apply for and are granted nationality by a court in Paraguay, there is a possibility that they acquire Paraguayan nationality. However, A and B have been stateless since birth and have been residing in Japan for more than three years. Therefore, they applied for naturalization in January 2016 based on Article 8(iv) of the Japanese Nationality Act; their applications were granted; and they acquired Japanese nationality in January 2017. (4) Administrative response by Japan The parents of A and B were confused by the discrepancies in nationality, as A and B were considered as non-nationals by the Embassy of Paraguay, but their foreigner residence cards in Japan showed “Paraguay” in the “Nationality/area of origin” column. The mother of A and B consulted the legal affairs bureau located in the Kanto region on several occasions regarding naturalization, but she was never informed that it was possible to apply for naturalization under the assumption that Article 8(iv) (the so-called “simplified naturalization”) would be applied, which eases the normal requirements for naturalization for stateless persons born in Japan. It was only when she consulted an attorney-at-law that she learned that her children would be able to make such applications, and she proceeded to go through the procedure. First, she made an application to the regional immigration bureau located in the Kanto region to correct the information shown on her children’s foreigner residence cards, i.e., to change their nationality from “Paraguay” to “Stateless”; however, she was told that the regional immigration bureau was not in a position to make a determination, and the correction was made only after more than four months had passed. In addition, C, who is the cousin of A and B on their father’s side, was also stateless; C’s (former) alien registration certificate as well as foreigner residence card showed 46