Shiikuwasha ( Citrus depressa Hayata) is a well-known traditional citrus fruit from Okinawa, with over 200 cultivars and varieties reported. The harvest season of Shiikuwasha is extensive, from August to February, and Shiikuwasha has a unique usage pattern. Unripe fruit, harvested in August and September, is used for cooking, while partially ripe fruit, available from October to December, is used for machining (mainly for juice) . Ripe fruit with reduced acidity is available in January and February and is used unmodified. Polymethoxylated flavones (PMFs) are characteristic components of Shiikuwasha. Depending on harvest time and variety, alterations in juice quantities, citric acid concentrations, and PMFs were observed. Most applications of Shiikuwasha involve juice processing. Notably, the efficiency of Shiikuwasha juice production is only about 50%. Many useful components are contained in the peel, and remain in the residue. A comparison of extraction methods revealed that a multi-stage extraction recovered more useful components. According to marketing research, consumer demand exists for products of Shiikuwasha as a seasoning. Therefore, we are developing applications (especially as seasonings) for juice residue containing essential oils and PMFs.