在日本，多數出租房屋的契約屬於「普通租賃契約」，也就是不定期租賃契約（更新型），這種制度的根源來自日本法律對租屋弱勢方—租客—的高度保護原則。根據《借地借家法》，即使租賃契約設定固定期限，例如兩年，當期限到達時，房東若要終止契約，並不能單方面要求租客搬離，而是必須有「正當事由」。所謂的正當事由，包含房東確實需要自住、重大裝修工程或是租客違反重大租約條款（如長期欠租、破壞房屋等），且這些事由必須經過法院判斷是否合理，否則租客有權利繼續居住，甚至可以主張續約。

這種制度導致「定期租賃契約」（定期借家契約）在日本實務上反而不普遍。因為定期租賃契約在法律上雖然到期即可終止，但要生效必須在簽約前由房東用書面明確告知租客「契約屆滿即不續約」，否則契約將被視為無效。而許多租客對此有所顧忌，擔心居住不穩定，會傾向拒絕此類契約，加上房東在招租時也不易吸引到穩定長期的租戶，因此實務上仍多採普通租賃契約。

此外，搬家成本高也是一大原因。在日本，搬家不僅費用高昂（包含禮金、押金、仲介費、清潔費、搬家公司費用等），且社會觀念上也習慣一住多年，不像有些國家會頻繁更換住處。因此若房東想中止租賃關係，就必須承擔足夠的賠償成本，甚至需要額外支付一筆所謂「立退料」，以補償租客因搬遷所產生的不便和損失。根據實務案例，若房東堅持終止租賃，所需支付的補償金往往接近一年甚至兩年的租金，進一步壓縮房東調整物業使用的彈性。

整體而言，日本租賃制度設計是為保障租客居住權，避免房東濫用權力任意漲租或驅逐住戶。因此多數租賃契約形式上雖為定期兩年，但實質上卻是默認續約的不定期狀態，使租客可以長期穩定居住。對房東而言，若希望使用「定期借家契約」方式收回物件，除非能提供明確且具有說服力的理由，否則將面臨法律與實務的多重挑戰。

In Japan, most rental housing contracts fall under what's known as an “ordinary lease agreement,” which is essentially a non-fixed-term (renewable) lease. This system is rooted in Japanese law's strong emphasis on protecting the weaker party in housing arrangements—the tenant. According to the Land and House Lease Law (借地借家法), even if a lease is set for a fixed term—such as two years—the landlord cannot unilaterally demand that the tenant move out once the lease expires. To terminate the lease, the landlord must present a justifiable reason. These reasons might include the landlord needing to move in themselves, carrying out major renovations, or the tenant violating serious terms of the agreement, such as long-term non-payment of rent or property damage. Furthermore, such justifications must be evaluated by the court to determine their validity. If the court deems the reasons insufficient, the tenant has the legal right to remain and may even request a lease renewal.

This legal structure makes “fixed-term lease agreements” (teiki shakuyaku keiyaku) relatively rare in practice. Although fixed-term leases can legally end without renewal, they are only valid if the landlord clearly informs the tenant in writing before the contract is signed that the lease will not be renewed upon expiration. Without this prior written notice, the agreement may be considered invalid. Many tenants hesitate to sign such contracts out of fear of housing instability, and landlords often find it harder to attract long-term, reliable tenants under such terms. As a result, the majority of rental agreements continue to use the ordinary lease format.

Another key factor is the high cost of moving in Japan. Relocating involves a significant financial burden—including key money, deposit, agent fees, cleaning charges, and moving company costs—and culturally, there is an expectation of long-term residence rather than frequent relocation. Therefore, if a landlord wishes to end a rental agreement, they often must bear a substantial compensation cost, sometimes referred to as “eviction money” (tattai-ryō), to cover the tenant’s inconvenience and losses. In practice, this compensation may amount to one or even two years’ worth of rent, which further reduces the landlord’s flexibility in reclaiming their property.

Overall, Japan’s rental system is designed to protect tenants’ right to stable living conditions and to prevent landlords from abusing their position by arbitrarily raising rent or evicting tenants. Although most contracts may state a two-year term, in reality, they are treated as renewable by default—creating a semi-permanent arrangement that favors tenant stability. For landlords wishing to regain possession of their property through a fixed-term lease, unless they can present a clear and convincing reason, they are likely to face both legal and practical obstacles.