Modifying Claims or Filing Counterclaims in a Japanese Civil Appeal: What Are the Rules?

Japanese Attorney at Law - Bengoshi L.L.

• 8 min read

The Japanese civil appeal (控訴 - kōso) system, operating as a "continuation system" (続審制 - zokushinsei), means that the appellate court essentially re-examines the case rather than merely reviewing the first-instance judgment for errors on a closed record. This continuation model theoretically allows for a degree of procedural dynamism, including the possibility for parties to modify their existing claims (訴えの変更 - uttae no henkō) or for defendants (now often appellees) to introduce new counterclaims (反訴 - hanso). However, introducing such new substantive elements at the appellate stage is not unrestricted and is governed by specific rules designed to balance flexibility with procedural fairness and efficiency.

Modifying Claims (訴えの変更) in a Japanese Civil Appeal

The ability for a plaintiff (often the appellant, or an appellee filing a cross-appeal) to modify their claim at the appellate stage is primarily governed by Article 143 of the Code of Civil Procedure (CCP), which applies to appeals through the general application provision of Article 297 CCP.

1. Core Conditions from Article 143 CCP:
A party may modify their claim provided that:

  • The "Basis of the Claim" Remains Unchanged (請求の基礎に変更がないこと - seikyū no kiso ni henkō ga nai koto): This is a crucial requirement. The modification should not introduce an entirely new and unrelated dispute. The "basis of the claim" refers to the underlying factual and social dispute or the core set of operative facts giving rise to the claim. If the modification merely changes the legal characterization of the same underlying grievance or adjusts the relief sought based on the same set of facts, the basis is generally considered unchanged.
  • No Significant Delay to Proceedings (訴訟手続を著しく遅延させないこと - soshō tetsuzuki o ichijirushiku chien sasenai koto): The modification should not unduly prolong the litigation. The appellate court will assess whether allowing the modification would necessitate extensive new evidence or arguments that could have been presented earlier, thereby unfairly delaying the resolution.
  • Up to the Conclusion of Oral Arguments: Such modifications can generally be made at any time until the conclusion of oral arguments in the appellate court.

The rationale for allowing claim modifications when the "basis of the claim" is the same is that the core factual dispute has likely already been examined to some extent by the first-instance court. Therefore, allowing modifications within this scope at the appellate level does not fundamentally prejudice the opposing party's right to have the essential dispute heard from the first instance.

2. When the "Basis of the Claim" Does Change:
If a proposed modification does alter the fundamental basis of the claim, introducing a substantially new dispute, the rules become stricter. In such cases, the modification is generally permissible only with:

  • The consent of the opposing party.
  • If the opposing party proceeds to argue the merits of the newly modified claim without raising an objection (this is often deemed an implied consent or waiver of the right to object).

This higher bar protects the opposing party from being forced to litigate an entirely new case for the first time at the appellate level, thereby preserving their "benefit of instance" (審級の利益 - shinkyū no rieki)—the right to have a matter adjudicated through two substantive factual instances if they so choose.

3. Specific Types of Claim Modification:

  • Expansion or Reduction of Claim (請求の拡張又は減縮):
    • Increasing the monetary amount sought (expansion) is a form of claim modification subject to the conditions above.
    • Reducing the claim (請求の減縮 - seikyū no genshuku) is also a modification. It is often legally characterized as a partial withdrawal of the lawsuit (訴えの一部取下げ) or a partial waiver of the claim (請求の一部放棄). A significant consequence is that the first-instance judgment concerning the reduced portion typically loses its effect, and the appellate court will only adjudicate the remaining part of the claim. For example, if a plaintiff was awarded ¥10 million and the defendant appeals, and the plaintiff then reduces their claim to ¥7 million in the appeal, the original judgment for the ¥3 million difference is effectively nullified with respect to that portion.
  • Changing Joinder Types: Modifying the way claims are joined, such as changing from a selective joinder (where the court chooses one of several claims) to a preliminary joinder (where claims are ranked), or vice-versa, is generally considered a permissible form of claim modification, subject to the usual conditions.

4. Appeal Must Be Validly Pending:
It's important to note that a party cannot file an appeal solely for the purpose of modifying a claim if they had no other legitimate grievance or basis for appealing the first-instance judgment. The appeal itself must first be admissible. The claim modification is then made within the framework of that validly pending appeal.

Filing Counterclaims (反訴 - Hanso) in a Japanese Civil Appeal: Stricter Rules

While claim modifications by the original plaintiff (or an appellant in that position) are governed by the general rules of Article 143 CCP, the introduction of a counterclaim by the original defendant (now typically the appellee, or an appellant if they were the original defendant) at the appellate stage is subject to more specific and stringent rules under Article 300 of the CCP.

1. Article 300 CCP: The Gatekeeper for Appellate Counterclaims:
This article specifically addresses "new" counterclaims filed for the first time in the appeal court.

2. Core Requirements for an Appellate Counterclaim:

  • Relatedness (関連性 - kanrensei): The counterclaim must be related to the main claim that was the subject of the first-instance proceedings or to the means of defense against that main claim. This requirement aims to ensure some coherence and prevent entirely unrelated disputes from being injected at the appellate stage.
  • No Significant Delay: Similar to claim modifications, the filing of the counterclaim must not cause undue or significant delay to the appellate proceedings.
  • The Opponent's Consent (相手方の同意 - aitekata no dōi) – The General Rule: This is the most critical and distinguishing requirement for appellate counterclaims. As a general rule, a new counterclaim at the appellate stage requires the consent of the opposing party (the original plaintiff, who is now the cross-appellee/counterclaim defendant).
    • Deemed Consent: If the opposing party, without raising an objection to the admissibility of the counterclaim, proceeds to argue on the merits of the counterclaim itself, their consent is deemed to have been given (Article 300(2) CCP).

The primary reason for requiring the opponent's consent is to protect their "benefit of instance" (shinkyū no rieki). A counterclaim is essentially a new lawsuit by the defendant against the plaintiff. Allowing it freely at the appellate stage would deprive the original plaintiff of the opportunity to have this new claim against them heard first by a court of first instance.

3. The Critical Exception to Consent: Counterclaims on the "Same Basis" as the Main Claim:
Despite the general consent requirement, a significant interpretation supported by case law and prevailing legal theory provides an important exception: if the counterclaim shares the same factual and legal basis (請求の基礎が同一 - seikyū no kiso ga dōitsu) as the original main claim, the opponent's consent is not required for it to be filed and considered by the appellate court.

  • Rationale: When the counterclaim arises from the very same underlying dispute or transaction as the main claim, the first-instance court, in adjudicating the main claim, has inevitably already dealt with the core factual matrix. Therefore, allowing a closely related counterclaim at the appeal stage does not unduly prejudice the original plaintiff's benefit of instance regarding this shared core subject matter. This aligns with the principles of procedural fairness and equality of arms, as plaintiffs can modify claims based on the same foundation without consent.

4. Other Scenarios and Considerations for Appellate Counterclaims:

  • "New" Counterclaims Only: Article 300 CCP applies only to counterclaims filed for the first time at the appellate stage. If a counterclaim was already filed and adjudicated (or pending) in the first instance, its review on appeal follows the general rules for appealing any part of the judgment, not Article 300.
  • Intermediate Declaratory Counterclaims: If a defendant raised a defense at first instance (e.g., asserting the existence of a lease agreement to counter an eviction claim), and wishes to seek a binding declaration on that specific legal relationship (e.g., a declaration that the lease exists) via a counterclaim at the appeal stage, such an "intermediate declaratory counterclaim" that relies on a defense already litigated might not require consent under Article 300.
  • Counterclaims Related to Provisional Execution: If the first-instance judgment was provisionally executed (仮執行 - kari-shikkō) and the defendant-appellant suffered damages or made payments as a result, a counterclaim in the appeal seeking restitution or damages arising from that provisional execution may be filed without the original plaintiff's consent, due to the specific nature and purpose of such claims within the execution context.
  • Procedural Route: A defendant who was entirely successful at first instance (i.e., the plaintiff's claim was dismissed) generally cannot file a primary appeal solely for the purpose of lodging a counterclaim. If the plaintiff appeals, the successful defendant (now appellee) can then file their counterclaim by way of a cross-appeal (附帯控訴 - futai kōso).

Interaction with the Scope of Appeal and "Grievance"

It is fundamental that for any modification of claim or new counterclaim to be considered, a valid appeal or cross-appeal must be properly before the appellate court. These procedural tools are not means to initiate an appeal if no underlying "grievance" (不服 - fufuku) against the first-instance judgment exists. The modifications or new claims are then advanced within the framework of that legitimately pending appellate proceeding.

The Court's Discretion and Prevention of Undue Delay

In all instances of proposed claim modifications or new counterclaims at the appellate stage, the court retains overall discretion to manage its proceedings. Even if a modification or counterclaim meets the basic requirements (e.g., same basis of claim, or opponent's consent), the court can still refuse to allow it if it concludes that doing so would genuinely and substantially disrupt or unreasonably delay the appellate process. This ensures that while flexibility is provided, it does not lead to an unmanageable or unfair protraction of the litigation.

Strategic Implications for Litigants

  • For Appellants (Original Plaintiffs): If new developments or a re-evaluation of the case warrants a change to the claim, the appellate stage offers an opportunity, especially if the "basis of the claim" remains consistent. However, a radical departure might require the appellee's consent.
  • For Appellees (Original Defendants): The appellate counterclaim, though subject to consent for entirely new matters, can be a powerful tool, especially if their counterclaim arises from the same factual matrix as the original claim. It allows for a comprehensive resolution of the dispute. Filing a cross-appeal is the standard vehicle for this.
  • Timeliness and Persuasion: Regardless of the specific rules, parties seeking to introduce new substantive matters at appeal should do so as early as possible and be prepared to cogently argue why it is permissible and will not unduly delay the proceedings, especially in the context of courts often aiming for efficient "post-hoc review."

Conclusion

The Japanese civil appeal system, through its "continuation model," provides avenues for parties to modify claims and, for defendants, to file counterclaims at the appellate stage. Modifications of claims by the plaintiff are generally permissible if the core basis of the claim remains the same and proceedings are not unduly delayed. New counterclaims by the defendant, however, face the additional hurdle of requiring the original plaintiff's consent, primarily to protect the plaintiff's right to a first-instance hearing on new claims against them. A significant exception to this consent requirement exists when the counterclaim shares the same fundamental basis as the plaintiff's original claim. These rules attempt to strike a balance, allowing for the evolving nature of disputes and ensuring comprehensive resolution, while safeguarding against unfair surprise and undue prolongation of litigation at the appellate level.