For the most part, parties have freedom of contract in Japan and are allowed to include, or not include, whatever they want in their contract. However, there are exceptions to this generally lenient rule and the mandatory provisions for contracts in Japan included in the Japan Civil Code are one exception.
These are mandatory provisions for contracts in Japan that are automatically inserted into the contract by law. One example is for contracts governing the lease of land for the purpose of owning a building. The Land Lease and House Lease Act provides that these contracts shall have a minimum term of 30 years. Therefore, the parties have freedom to contract for longer than 30 years, but are prohibited from contracting to any smaller period of time. Usually these mandatory provisions for contracts in Japan are created to protect the weaker contracting party but it is important for both contracting parties to be aware of them.