Understanding "Partial Claims" (Ichibu Seikyū) in Japanese Case Law: What is the "Explicit Statement" Theory and When Can You Pursue the Remainder?

Japanese Attorney at Law - Bengoshi L.L.

• 10 min read

In Japanese civil litigation, a plaintiff may sometimes choose to sue for only a portion of a larger, quantitatively divisible claim—such as a monetary debt or a series of quantifiable damages—while reserving the right to sue for the remaining portion at a later date. This is known as a "partial claim" (ichibu seikyū - 一部請求). The central legal question arising from this strategy is: under what circumstances can the plaintiff subsequently bring a lawsuit for the reserved remainder (zanbu seikyū no kahi - 残部訴求の可否)? Japanese case law has developed a nuanced approach to this issue, often referred to as the "Explicit Statement Theory" (meijisetsu - 明示説). However, as we will explore, this theory is far from a simple rule and involves complex interactions with the principles of res judicata (既判力 - Kihanryoku) and good faith (shingi-soku - 信義則).

The Traditional "Explicit Statement Theory" (Meijisetsu) and its Interaction with Res Judicata

The foundational principle of the "Explicit Statement Theory," as established by early Supreme Court precedents, centers on the plaintiff's declaration regarding the scope of their claim in the initial lawsuit.

Core Principle: The Effect of an "Explicit Statement" (Meiji)

If a plaintiff, when filing the first lawsuit, clearly and explicitly states (meiji - 明示) that they are claiming only a specific part of a larger divisible claim and are reserving the right to pursue the remainder later, the subject matter of litigation (soshōbutsu - 訴訟物) of that initial suit is considered to be only the explicitly claimed portion. This was articulated in a key Supreme Court judgment on August 10, 1962 (Minshu Vol. 16, No. 8, p. 1720).

The direct consequence of this delineation of the soshōbutsu relates to res judicata. The res judicata (the binding, preclusive effect) of the judgment rendered in the first (partial) claim attaches only to that specifically claimed and adjudicated part. It does not extend to the reserved remainder, which was not part of the soshōbutsu of the first action. Therefore, the general outcome under this traditional understanding is that the plaintiff is free to file a subsequent lawsuit for the reserved remainder. This second lawsuit is considered to have a different soshōbutsu and is thus not barred by the res judicata of the first judgment.

The Default Scenario: When No Explicit Statement is Made

Conversely, if a plaintiff sues for an amount that is objectively less than their total potential claim but does without explicitly stating that it is a partial claim and without expressly reserving the right to sue for the remainder, the traditional starting point was more restrictive. An early influential case, Supreme Court, June 7, 1957 (Minshu Vol. 11, No. 6, p. 948), dealt with a situation where a plaintiff, having overlooked that a debt was joint and several, sued one debtor for only half the amount (believing it to be the full extent of that debtor's several liability), without indicating this was a partial claim against a larger joint obligation. When the plaintiff later attempted to sue for the other half, asserting the joint and several nature of the debt, the Supreme Court treated the first claim as having encompassed the entire subject matter as then understood and pursued by the plaintiff. Consequently, the res judicata of the first judgment was held to bar the subsequent claim for the "remainder."

This led to a common, albeit simplified, understanding: if an explicit statement of partial claim and reservation is made, the remainder can be sued for; if no such explicit statement is made (an "implied" or silent situation), the first claim is presumed to cover the entire dispute then presented, and res judicata bars a subsequent claim for any remainder. However, subsequent Supreme Court jurisprudence has significantly refined this, demonstrating that the reality is more complex.

Exceptions and Nuances: Moving Beyond a Simple "Explicit Statement" Dichotomy

The practical application of the "Explicit Statement Theory" has evolved. It's now clear that the presence or absence of a literal "explicit statement" is not the sole determinant. Courts, particularly the Supreme Court, have introduced considerations of good faith and have engaged in a more evaluative approach based on the overall circumstances.

A. Even with an Explicit Statement, a Remainder Suit May Be Barred by Good Faith (Shingi-soku)

A pivotal development came with the Supreme Court judgment of June 12, 1998 (Minshu Vol. 52, No. 4, p. 1147). This case established that even when a plaintiff has made an explicit statement that their claim for a quantitatively divisible monetary debt is only partial, a subsequent lawsuit for the remainder might still be barred, not by res judicata, but by the Principle of Good Faith (shingi-soku - 信義則).

The Scenario and Rationale of the 1998 Supreme Court Case:
Imagine a plaintiff makes an explicit partial claim for a sum of money. In adjudicating this partial claim, the court inevitably has to examine the basis and existence of the entire alleged underlying debt to determine if even the partial amount is due. If the court, after such a comprehensive examination, dismisses the partial claim (either wholly or in part) on its merits, this implies a finding about the larger debt (e.g., that the entire debt does not exist, or is less than the partial amount claimed, meaning no remainder could logically exist).

In such a situation, the Supreme Court reasoned:

  • The defendant, having gone through a trial where the entirety of the underlying debt was effectively scrutinized, would form a reasonable expectation that the dispute regarding that entire debt has been conclusively resolved.
  • Allowing the plaintiff to then file a new lawsuit for a supposed remainder, after the initial partial claim (which itself was based on the same underlying debt) was found wanting, would subject the defendant to a duplicative burden of defense and would be unfair.
  • Therefore, bringing such a remainder suit, despite the initial explicit statement, would be contrary to the Principle of Good Faith and thus impermissible (usually leading to a dismissal of the subsequent action as inadmissible - uttae kakka - 訴え却下).

This 1998 judgment demonstrates that an "explicit statement" is not a foolproof guarantee for the admissibility of a remainder suit. The substance of the first adjudication and considerations of fairness to the defendant can override the formal separation of soshōbutsu that an explicit statement typically achieves.

B. Even without a Direct Explicit Statement, a Remainder Suit May Be Permitted: The Evaluative Nature of "Explicit Statement"

Conversely, there are situations where, even in the absence of a direct, literal "explicit statement" of partial claim and reservation, courts have permitted subsequent suits for what amounts to a remainder. This often occurs when circumstances make it unjust to preclude the plaintiff from seeking further redress. In these instances, the "explicit statement" concept is treated not as a requirement for a specific verbal formula, but as a conclusion reached through a judicial evaluation of the entire context of the first lawsuit.

  1. Later-Developing, Unforeseeable Damages:
    Japanese courts have shown flexibility in cases involving damages that were genuinely unforeseeable at the time of the initial lawsuit.In both these types of cases, the plaintiffs had not made an explicit, formal statement in the first suit reserving their rights for these specific, unforeseeable future developments. The courts, through an evaluative lens, construed the initial claims as inherently limited by the scope of what was knowable and claimable at the time, thereby allowing subsequent actions for the "new" or "expanded" portions of the harm. This is less about finding a missed "act" of explicit statement and more about a judicial construction to prevent substantive injustice.
    • Latent Injuries or Later-Appearing After-Effects (kōhatsu kōishō - 後発後遺症): The Supreme Court decision of July 18, 1967 (Minshu Vol. 21, No. 6, p. 1559) involved a personal injury claim. After the initial judgment, the plaintiff developed new, unexpected medical conditions stemming from the original injury that required further treatment and generated additional damages. The Court allowed a subsequent suit for these new damages. It reasoned that the first claim, which covered damages known or foreseeable up to the conclusion of the first trial, was retrospectively evaluated as having been an "implicit partial claim" with respect to these later, unforeseeable damages. The soshōbutsu were thus deemed different.
    • Expanded Damages (kakudai songai - 拡大損害): Similarly, in a case involving ongoing damages (e.g., loss equivalent to rent due to unlawful occupation of land), the Supreme Court on July 17, 1986 (Minshu Vol. 40, No. 5, p. 941) permitted a new lawsuit for an increased amount of damages when, due to subsequent, unforeseeable circumstances like significant inflation or a surge in land values, the rate of damages awarded in the first judgment became demonstrably inadequate. The Court reasoned that the initial claim was implicitly understood to exclude such unforeseeable future escalations, effectively rendering the first claim "partial" in nature concerning these later expansions.
  2. "Specified Partial Claims" (Tokutei Ichibu Seikyū - 特定一部請求) and Inferring an "Explicit Statement":
    The Supreme Court has also considered situations where a plaintiff claims for only certain specified items of a larger, multi-item claim (e.g., in a tort case, claiming only for medical expenses while other damage categories like lost income or pain and suffering also exist and are potentially quantifiable).
    The Supreme Court judgment of July 10, 2008 (Saibanshu Minji No. 228, p. 463) addressed such a scenario. It held that even without a direct verbal incantation like "this is a partial claim for only medical expenses," an "explicit statement" of a partial claim (with respect to the unmentioned but related items) could be inferred or evaluated from the totality of the circumstances. Factors that might lead to such an evaluation include:This evaluative approach is strongly guided by considerations of good faith: was the defendant reasonably led to believe that the first suit was a complete and final settlement of all potential claims arising from the event, or did the circumstances suggest that further claims might be forthcoming? If the defendant could not reasonably have expected absolute finality, then treating the first, limited claim as "explicitly partial" (in effect) can be deemed fair.
    • The plaintiff's clear specification and quantification of only the claimed items, implying that other known or potential items are, for the time being, not being pursued.
    • The claimed items being substantively distinct and separable from other potential categories of claims arising from the same incident.
    • Genuine practical difficulties for the plaintiff in comprehensively identifying, quantifying, and pursuing all potential items of the claim simultaneously in the first action.
    • The defendant's awareness, or reasonable foreseeability from the nature of the dispute, that other related claims or damage categories might exist and could be pursued later.

The "Explicit Statement Theory": An Evaluative Framework, Not a Rigid Rule

Synthesizing these developments, the "Explicit Statement Theory" (meijisetsu) in modern Japanese case law is not a simplistic, rigid rule based solely on whether the plaintiff uttered specific words of reservation. It functions more as a flexible, evaluative framework. The court considers a range of factors:

  • Plaintiff's Manifestations: This includes direct statements of partial claim and reservation, but also conduct, the structure of pleadings, and the specificity of the claims made, from which an intention to claim partially might be inferred.
  • Nature of the Claim: Is it a single, indivisible monetary sum, or is it a complex set of damages or obligations that naturally unfold or become quantifiable over time?
  • Foreseeability: Was the remaining portion of the claim reasonably foreseeable and quantifiable at the time of the first lawsuit?
  • Defendant's Reasonable Expectations: Based on the plaintiff's conduct and the nature of the first suit, could the defendant reasonably believe that the first judgment represented a final resolution of the entire underlying dispute?
  • Overall Fairness and Equity: Guided by the Principle of Good Faith (shingi-soku), the court seeks a solution that is fair to both parties, preventing plaintiffs from being unjustly deprived of their full remedy for unforeseeable developments, while also protecting defendants from vexatious or unfairly duplicative litigation.

General Presumptions and Exceptions:

  • With a Direct Explicit Statement: The presumption is that the remainder can be pursued, as res judicata does not bar it. However, this is subject to the good faith limitation highlighted by the 1998 Supreme Court decision: if a partial claim for a quantifiable monetary sum is dismissed on merits that effectively negate the entire underlying debt, a subsequent remainder suit may be barred by good faith.
  • With No Explicit Statement (Implied or Silent Partial Claim): The initial presumption leans towards the first claim having covered the entire dispute then cognizable by the plaintiff, meaning res judicata from the first judgment might bar a subsequent attempt to re-litigate or expand that same soshōbutsu. Exceptions to this are recognized, primarily by judicially evaluating the first claim as having been implicitly partial, especially in situations involving:
    • Genuinely unforeseeable later-developing damages (as in the 1967 and 1986 Supreme Court cases).
    • Circumstances where the defendant could not reasonably have expected the first, limited suit to be the final word on all related matters (as in the 2008 Supreme Court case on specified partial claims).

Strategic Implications for Litigants

This nuanced doctrine carries important strategic considerations:

  • For Plaintiffs:
    • If you intend to pursue a claim in stages, the most prudent approach is to make a clear, unambiguous, and explicit statement in your initial pleadings that it is a partial claim and that you reserve the right to sue for the remainder. This creates the strongest basis for arguing that the soshōbutsu are separate.
    • However, be acutely aware of the 1998 Supreme Court precedent. Even with an explicit reservation, if your explicitly partial claim for a monetary sum is dismissed on merits that effectively find the entire underlying debt non-existent or already satisfied, a subsequent remainder suit is vulnerable to a challenge based on the Principle of Good Faith.
    • In cases of potentially evolving or later-manifesting damages, meticulously document the reasons why such damages were unforeseeable or unquantifiable at the time of the first lawsuit.
  • For Defendants:
    • If you are faced with a claim that appears to be only a portion of what the plaintiff could claim, but lacks an explicit statement of reservation, assess whether the circumstances might lead a court to nonetheless evaluate it as a partial claim (e.g., if it's a "specified partial claim" for only certain damage items).
    • If the claim is explicitly partial, be prepared for the possibility of a subsequent suit for the remainder.
    • Crucially, if an explicitly partial claim (especially for a sum of money) is dismissed after a full examination of the entire underlying debt, the 1998 Supreme Court judgment provides strong grounds to argue that any subsequent attempt to sue for a remainder would be contrary to good faith.

Conclusion: A Flexible Doctrine Rooted in Substantive Fairness

The Japanese judiciary's approach to partial claims and the subsequent pursuit of remainders is not governed by a simple, mechanical rule. The "Explicit Statement Theory," while ostensibly hinging on the plaintiff's declaration, is deeply interwoven with the foundational principles of res judicata, the equitable considerations of the Principle of Good Faith, and an overarching judicial evaluation aimed at achieving a resolution that is both procedurally sound and substantively fair in the specific circumstances of each case. Courts endeavor to strike a balance: allowing plaintiffs a fair opportunity to pursue their legitimate claims in full, especially when components of those claims are initially unforeseeable or difficult to quantify, while simultaneously protecting defendants from the burdens of unfairly duplicative litigation and upholding the important societal interest in the finality of judgments.