An obi is a traditional Japanese sash worn with a kimono, which is a formal garment. It is typically made from silk or other fine fabrics and can be quite decorative, featuring intricate patterns and colors. The obi serves both a functional and aesthetic purpose, helping to secure the kimono in place while also adding to the overall beauty of the outfit. Obi come in various styles and widths, depending on the occasion and the type of kimono being worn. For example, a fukuro obi is a more formal type, often used for special events, while a haneri is a narrower version typically worn with casual kimonos.