Legally, Japan does not officially allow dual citizenship for adults. According to the Japanese Nationality Act, any Japanese citizen who holds a second nationality must choose one before they reach the age of 22 (or within two years of acquiring a second nationality if it happened after age 20). If a Japanese citizen voluntarily acquires a foreign nationality (for example, by naturalizing in the U.S. or Canada), they automatically lose their Japanese citizenship under Article 11 of the law. However, for those born with dual citizenship (such as a child with one Japanese and one foreign parent), the reality is a "grey zone" of tolerated ambiguity. While the law requires them to submit a "Nationality Selection Form" (選択届), the Japanese government has historically been very lax in enforcing the renunciation of the other nationality. There are no criminal penalties for failing to choose, and the government rarely takes the drastic step of stripping someone of their birthright citizenship. That said, as of 2026, the official stance remains "one nationality only," and those who naturalize as Japanese later in life are strictly required to provide proof that they have renounced their original citizenship, making the "dual citizen" experience one of informal tolerance rather than legal acceptance.