Precision in identifying the location of a property is a cornerstone of any reliable land registration system. In Japan, the official "location" (shozai, 所在) of a parcel of land recorded in the Real Property Registry is meticulously defined, often extending to traditional administrative subdivisions that might not always be apparent in everyday postal addresses. One such subdivision is the koaza (小字), or minor section name. A key directive from Japan's Ministry of Justice, issued on January 11, 1966 (Showa 41), clarified the necessity of including these minor section names, underscoring the system's commitment to precise parcel identification.

Understanding Japanese Geographic Subdivisions for Land Registration

To appreciate the role of koaza, it's helpful to understand the typical hierarchy of administrative and geographic divisions used in Japanese land registration:

1. Prefecture (県 - ken, 都 - to, 道 - dō, 府 - fu): The largest administrative division.
2. Municipality (市町村 - shichōson): This includes Cities (市 - shi), Towns (町 - machi or chō), and Villages (村 - mura or son). Larger cities are often subdivided into Wards (区 - ku). Some rural areas are organized into Counties (郡 - gun), which historically contained towns and villages.
3. Aza (字): These are traditional subdivisions within a town or village, or older sections of a city. Aza often carry historical significance, reflecting old village names, geographical features, or traditional land use patterns. There are generally two types:
   • Ōaza (大字): Larger sections, which might correspond to former villages or significant historical areas that were later incorporated into a larger municipality.
   • Koaza (小字): Smaller, more localized sections, often found within an ōaza or directly within a town or village that doesn't have ōaza. A single ōaza can contain multiple koaza.
4. Chiban (地番): This is the lot number assigned to an individual parcel of land.

The crucial concept for lot numbering is the Chiban Kuiki (地番区域 - lot numbering area). As defined in Article 97 of the Real Property Registration Rules, this is the specific geographic unit (e.g., a city, ward, town, village, ōaza, or other designated area) within which each chiban is unique and lot numbers are typically assigned sequentially or according to a systematic plan.

The question addressed by the 1966 directive revolved around the level of aza detail required in the registered location if a larger aza (like an ōaza) already served as the chiban kuiki.

The 1966 Ministry of Justice Directive: The Mandate for Koaza Inclusion

The legal basis for recording location details stems from the Real Property Registration Act. Article 34, Paragraph 1, Item 1 specifies that for land, the registration must include the city, ward, county, town, village, and aza where the land is situated. Similarly, for buildings, Article 44, Paragraph 1, Item 1 requires the city, ward, county, town, village, aza, and the lot number of the land on which the building stands. This information is recorded in the "Location" field of the heading section (表題部 - hyōdaibu) of the property register.

The Inquiry (Showa 40, 1965):
The Chief of the Utsunomiya District Legal Affairs Bureau posed a query to the Ministry of Justice. The scenario was as follows: If a specific ōaza, let's call it "Ōaza H," served as the official chiban kuiki (meaning lot numbers were unique within Ōaza H), and Ōaza H itself contained smaller, named sections, or koaza (e.g., "Koaza T" located within Ōaza H), was it sufficient to register the location as simply "Ōaza H," or was it mandatory to also include "Koaza T" in the official registered location? The argument for potential omission was that since Ōaza H defined the lot numbering area, perhaps the more granular koaza was redundant for unique identification purposes.

The Ruling (Showa 41, 1966):
The Director-General of the Civil Affairs Bureau of the Ministry of Justice provided a clear answer on January 11, 1966. The reply stated unequivocally that the koaza (in the example, "Koaza T") must be included in the registered location. The official wording indicated, "We believe the recording of the aza [interpreted in this context as the koaza] is necessary."

Rationale for Mandatory Inclusion:
The core reasoning behind this directive is the paramount importance of ensuring the maximum possible precision in identifying and locating each parcel of land within the registration system.

• While an ōaza might serve as the boundary for unique lot numbering, the koaza provides an additional, finer layer of geographic specificity. In areas with many parcels or complex layouts, this added detail can be crucial for distinguishing one property from another, especially if lot numbers alone might seem similar or follow complex patterns.
• Historically, land administration in Japan, even predating the modern registration system (e.g., under the old Land Ledger Act - 旧土地台帳法), recognized these smaller subdivisions. The 1966 directive essentially confirmed that this level of detail should be maintained for consistency and clarity. The aim was to prevent any ambiguity that might arise from omitting a recognized, albeit smaller, traditional administrative division.

Why is Koaza Inclusion Important for the Integrity of the Registry?

The insistence on including koaza names, even when they are subdivisions of a larger chiban kuiki, serves several important functions:

1. Enhanced Locational Accuracy: In many rural and older urban areas, koaza names are deeply ingrained in the local understanding of geography. They can be more intuitive for local residents and professionals than relying solely on broader area names and lot numbers. For instance, two parcels in the same ōaza with similar chiban could be miles apart, but their distinct koaza names would immediately clarify their different locations.
2. Historical and Cadastral Continuity: Koaza often reflect historical land ownership patterns, former village boundaries, natural geographical features (e.g., "upper field," "riverside plot"), or specific types of land use. Including them in the official registration preserves a link to this cadastral heritage and can be invaluable in historical property research or boundary dispute resolution.
3. Prevention of Ambiguity and Support for Unique Identification: The fundamental goal of a land registry is to provide an unambiguous record of each parcel. While the chiban is unique within its chiban kuiki, the koaza adds another layer to this uniqueness, reducing any potential for confusion with parcels in adjacent koaza or when dealing with very large and complex ōaza. This detailed specification supports the "individuality of the parcel" principle.
4. Consistency in Official Records: The practice of recording land down to the koaza level was already established in earlier land administration systems, such as the Land Ledgers. The 1966 directive ensured that the modern real property registration system maintained this level of detail, promoting consistency across different types of official land records.

Koaza and Modern Addressing Systems (Jūkyo Hyōji)

It is important to distinguish the official registered location (shozai) of land, which includes the koaza, from the modern addressing system used for mail and everyday navigation in many urbanized parts of Japan, known as the jūkyo hyōji (住居表示) system. The jūkyo hyōji system is typically based on city blocks, street names, and building numbers (e.g., Chiyoda-ku, Marunouchi 1-chōme 1-ban 1-gō).

The implementation of a jūkyo hyōji system in an area does not automatically abolish or replace the traditional ōaza and koaza for the purposes of land registration. The Legal Affairs Bureau continues to use the official cadastral location, including ōaza and koaza as applicable, along with the chiban, to identify land parcels in the registry. Therefore, a property might have two distinct "addresses":

• Its jūkyo hyōji address for postal and general locational purposes.
• Its official registered shozai (including koaza) in the land registry, which is the definitive legal identifier for the land parcel itself.

Practical Implications and Due Diligence

For legal professionals and businesses involved in Japanese real estate, the requirement to include koaza has several practical implications:

• Accurate Property Identification: When conducting due diligence, it is crucial to obtain the full and correct registered shozai from the land registry, including all ōaza and koaza elements. Relying solely on common-use or postal addresses can lead to misidentification or incomplete understanding of the property's official designation.
• Interpreting Registry Documents and Maps: Official registry extracts (tōkibo tōhon or tōki jikō shōmeisho) and official maps will use this full shozai. Understanding this detailed nomenclature is essential for correctly interpreting these documents.
• Historical Research: In complex cases, tracing the history of a parcel might involve understanding how koaza boundaries or names may have evolved, particularly in areas affected by past municipal mergers (shichōson gappei) or administrative redistricting.
• Challenges: While koaza enhance precision, they can also present challenges. Some koaza names may be archaic or not widely known today. Their exact boundaries might not always be clearly depicted on all modern maps, requiring reference to older cadastral maps or specialized knowledge.

Conclusion: Upholding Precision in Land Identification

The 1966 (Showa 41) Ministry of Justice directive, by affirming the necessity of including koaza (minor section names) in land registration records, reinforced the Japanese legal system's longstanding commitment to meticulous and unambiguous property identification. Even if a larger administrative unit like an ōaza forms the basis for unique lot numbering, the koaza provides an indispensable further layer of specificity. This detail, rooted in historical land administration practices, ensures that each parcel of land is defined with the highest possible degree of accuracy in the official registry. While modern addressing systems serve daily convenience, the traditional and detailed shozai, inclusive of koaza, remains the definitive legal identifier for land in Japan, underpinning the security and reliability of real property transactions.