Sudachi

Sudachi (Citrus sudachi; Japanese: スダチ or 酢橘) is a small, round, green citrus fruit of Japanese origin that is a specialty of Tokushima Prefecture in Japan. It is a sour citrus, not eaten as fruit, but used as food flavoring in place of lemon or lime. Genetic analysis shows it to be the product of a cross between a yuzu and another citrus akin to the koji and tachibana orange.