As a signee to the WTO Agreement on Government Procurement (GPA) Japanese government organisations must adhere to established international rules, if it concerns large tenders above a certain threshold. Thresholds are usually calculated in SDRs or Special Drawing Rights. The yen-equivalents of these amounts are adjusted regularly.
The height of the thresholds depends on the type of service or goods purchased and the kind of organisation that is purchasing. Thresholds for tenders issues by the central government are the lowest, while regional and local governments employ high thresholds. For instance, if you are planning to bid on a WTO tender concerning the purchase of a good or service (not construction related), the threshold is currently 100,000 SDRs which is equivalent to 13 million JPY. (About 93,000 Euro)
Information about the current is available here.