koshian is a type of sweet red bean paste commonly used in Japanese cuisine. It is made from adzuki beans that are cooked, sweetened with sugar, and then pureed to create a smooth texture. Koshian is often used as a filling for various traditional Japanese sweets, such as mochi and dorayaki. Unlike tsubuan, which has a chunky texture, koshian is completely smooth, making it ideal for desserts that require a refined consistency. It is popular in both modern and traditional Japanese confections, providing a rich, sweet flavor that complements many dishes.