Shirako (白子) refers to the milt (sperm sacs) of male fish and is highly prized as a delicacy in Japanese cuisine. Among the varieties, shirako from pufferfish (fugu) and cod (madara) is particularly prominent, often sold as standalone products. Cod shirako is known as "kumo-ko" (雲子) or "kiku-ko" (菊子) due to its unique shape, with kumo-ko meaning "cloud" in Japanese, as it resembles fluffy clouds. In Hokkaido, cod shirako is also referred to as "tachi". In Japanese cuisine, shirako is prepared and enjoyed in diverse ways, including shirako ponzu (lightly boiled and served with ponzu sauce), yaki-shirako (grilled), and shirako tempura (deep-fried). Cod shirako is particularly prized in winter, its peak season, and is known for its rich, creamy flavor. Shirako is also highly nutritious, rich in vitamins, minerals, and high-quality protein. Pufferfish shirako is even more valuable than cod shirako and is regarded as a luxury ingredient in Japanese fine dining.