Recently, the "cost increase of ingredients" has been listed as the critical management issue in \Ryokans ”(traditional Japanese inns). The characteristics of food inventory management in the Ryokan business are considered, namely, the high proportion of fresh ingredients in Ryokans" meal service, purchasing price ?uctuations, and the freshness of ingredients. Inventory management of fresh ingredients, by their nature,usually confront the reality of dynamic purchase prices and deterioration. This paper considers inventory models to decide the special order quantity of fresh ingredients in the Ryokan business domain when the supplier offers a one-time-only lower price. In this study, the concept of depreciation in corporate accounting is introduced to de?ne deterioration. Numerical examples using real data from Ryokan A in Tsukuba City are presented to con?rm the usefulness of the proposed model.