Did I Infringe? Key Elements of Copyright Infringement in Japan (Reliance and Similarity)

Understanding whether an act constitutes copyright infringement is a critical concern for any business or individual creating or utilizing content. In Japan, like in many other jurisdictions, copyright infringement is not a matter of strict liability for simply producing something similar to a pre-existing work. Instead, Japanese copyright law (著作権法 - Chosakuken-hō) requires a plaintiff to establish several key elements to succeed in an infringement claim. While a full infringement analysis involves assessing whether a valid copyrighted work exists and whether an exclusive right has been violated, this article focuses on two pivotal components that often form the crux of infringement disputes: reliance (依拠 - ikyo), essentially meaning the act of copying, and similarity (類似性 - ruijisei), or the degree to which the defendant's work resembles the plaintiff's protected work.

An Overview of Copyright Infringement Requirements in Japan

Before diving into reliance and similarity, it's useful to understand the general framework. To establish copyright infringement in Japan, a claimant typically needs to demonstrate:

1. The existence of a valid copyrighted "work" (著作物 - chosakubutsu) belonging to the plaintiff.
2. That the defendant relied upon (copied from) the plaintiff's copyrighted work to create their own work.
3. That the defendant's work is similar to the plaintiff's copyrighted work in its protected elements.
4. That the defendant performed an act that falls within the scope of the plaintiff's exclusive rights (e.g., reproduction, public transmission, adaptation).

This article will concentrate on the second and third elements: reliance and similarity.

Element 1: Reliance (依拠 - Ikyo) – The Copying Requirement

The concept of "reliance" is fundamental to copyright infringement in Japan. It means that the defendant's allegedly infringing work must have been created based on or derived from the plaintiff's copyrighted work. Independent creation, even if it results in a strikingly similar work, does not constitute copyright infringement under Japanese law.

What is Reliance and Why is it Necessary?

Reliance signifies that the defendant did not create their work independently but rather used the plaintiff's work as a source. The rationale for this requirement is deeply rooted in the nature of copyright and the desire to encourage creativity:

• Protection for Independent Creators: Copyright in Japan arises automatically upon creation without the need for registration. If mere similarity could lead to infringement, independent creators who coincidentally produce similar works could face unforeseen liability, which would stifle creativity. The reliance requirement ensures that only those who have actually copied are held liable.
• Balancing Interests: While copyright protects authors, it also aims to promote cultural development. Allowing liability for coincidental similarity would overly restrict the creative endeavors of others. The reliance doctrine ensures that an author's rights are not overextended to works not derived from their own.

It is important to distinguish reliance from mere "access." While proof of the defendant's access to the plaintiff's work is often a crucial step in proving reliance, access alone is not reliance. The core question is whether the defendant independently created their work or if it was derived from the plaintiff's work. For example, if a creator independently develops a work and subsequently becomes aware of a similar pre-existing work, their continued use of their independently created work would not constitute infringement due to a lack of reliance at the time of creation.

Proving Reliance in Practice

Direct evidence of copying (e.g., an admission by the defendant) is rare. Therefore, Japanese courts often permit reliance to be proven circumstantially. The burden of proof generally lies with the copyright holder alleging infringement.

Common methods to infer reliance include:

1. Proof of Access plus Similarity: If the defendant had a reasonable opportunity to access the plaintiff's work, and the two works are found to be similar, courts may infer that the defendant copied the plaintiff's work. The degree of similarity required to support this inference often depends on the uniqueness of the plaintiff's work and the extent of access. The PDF material mentions cases where access was inferred due to actual receipt of the plaintiff's work or wide distribution of the plaintiff's work when the defendant had a similar purpose.
2. Striking Similarity: In some cases, the similarities between the works may be so striking and particular (especially in arbitrary or non-functional elements) that any explanation other than copying is improbable, even if direct proof of access is weak.
3. Common Errors, "Traps," or Idiosyncrasies: The presence of identical errors, unusual features, or deliberate "traps" (e.g., fictitious entries in a dictionary or map) in both the plaintiff's and defendant's works can be compelling evidence of copying and thus reliance. For example, shared typographical errors in geographical maps have been used to infer reliance.
4. Similarity of Unprotected Elements as Circumstantial Evidence: While ideas, facts, or common themes are not themselves protected by copyright, a high degree of similarity in such unprotected elements, particularly if presented in a similar sequence or structure alongside protected expression, might circumstantially support an inference that the defendant also relied on the protected expression of the plaintiff's work.

Defendants can rebut an inference of reliance by providing evidence of independent creation, such as development records, prior art that explains similarities, or proof that they copied from a different, legitimate source.

What Must Be Relied Upon? The Object of Reliance

For copyright infringement to occur, the reliance must be on the creative expression of the plaintiff's work, not merely on its underlying ideas, facts, or public domain components.

• Reliance on Creative Expression: The defendant must have copied the specific way the plaintiff expressed their thoughts or sentiments – the copyrightable elements.
• No Infringement for Reliance on Ideas: If a defendant only takes the unprotectable ideas, concepts, historical facts, or functional aspects from a work and creates their own independent expression, there is no infringement, even if the defendant was inspired by or learned these ideas from the plaintiff's work. The Gateball Rulebook case (Tokyo District Court, Hachioji Branch, February 10, 1984) is illustrative: while the defendant's gateball rulebook was influenced by the plaintiff's original rules (the idea of the game), the court found no copyright infringement because the defendant had created their own expression of those rules, particularly as the game itself had evolved and was being played with various rule sets by then.
• Reliance on Derivative Works or Infringing Copies: It is also important to note that reliance can be established even if the defendant copied from a derivative work (二次的著作物 - nijiteki chosakubutsu) of the plaintiff's original work, or from an infringing copy. In such instances, the defendant is still, albeit indirectly, accessing and reproducing the creative expression of the plaintiff's original work that persists in the derivative or copied version. For example, if someone translates an English novel into Japanese (a derivative work) and a third party then copies significant portions of that Japanese translation, the third party may infringe both the translator's copyright in the translation and the original English author's copyright in the underlying novel.
• Serialized Characters (e.g., in Manga): Japanese courts have addressed situations involving the copying of characters from long-running series, like manga. Even if the specific comic panel or illustration that was copied cannot be pinpointed, infringement can be found if it's evident that the defendant's depiction of the character was derived from the plaintiff's copyrighted series. This analysis can become particularly intricate when considering works where early installments may have entered the public domain due to the expiration of copyright, while later installments remain protected. The Supreme Court decision in the Popeye case (July 17, 1997) dealt with such complexities, holding that for a serialized comic where each installment is a separate work, the copyright term for a character's depiction is based on its first appearance. If that initial copyright has expired, subsequent similar depictions in later installments, if they don't add new creativity to that specific character's appearance, might not be protected against copying of that original appearance.

Element 2: Similarity (類似性 - Ruijisei) – The Scope of Protection

Once reliance is established or inferred, the next critical inquiry is whether the defendant's work is "similar" to the plaintiff's work to an extent that constitutes infringement. This "similarity" is not a vague, overall resemblance; rather, it focuses on whether the defendant has reproduced a substantial part of the plaintiff's creative expression.

What Constitutes Actionable Similarity? The "Commonality of Creative Expression" Standard

The core principle guiding the similarity analysis in Japan is that copyright protects "creative expression" (Article 2, Paragraph 1, Item 1 of the Copyright Act). Therefore, for infringement to be found, there must be a "commonality of creative expression" (創作的表現の共通性 - sōsakuteki hyōgen no kyōtsūsei) between the plaintiff's work and the defendant's work. This means that the parts of the works that are similar must be parts that are original to the plaintiff and constitute protected expression, not merely shared ideas, facts, common knowledge, or unoriginal elements.

Evolution of Judicial Standards for Similarity

Japanese courts have refined their approach to assessing similarity over time:

1. Early "Sufficient to Perceive Content and Form" Standard: An early standard, articulated in cases like One Rainy Night in Tokyo (Supreme Court, September 7, 1978), suggested that reproduction meant recreating something "sufficient to allow perception of its content and form". This broad wording, however, could potentially lead to finding infringement even if only ideas or uncreative aspects were common.
2. "Direct Perception of Essential Features" Standard: The Parody case (Supreme Court, March 28, 1980), primarily a moral rights case concerning the right of integrity, stated that using another's work without permission is only allowed if it's done in a manner that does not allow "direct perception of the essential features of the expression format" of the original work. While influential, this standard also faced criticism for potential vagueness regarding what "essential features" meant and could lead to finding infringement based on similarities in unprotected elements.
3. Current Leading Standard: "Commonality of Creative Expression": The Supreme Court decision in the Esashi Oiwake folk song case (June 28, 2001) is a landmark in this area. It clarified that if a work created based on an existing work shares only "ideas, sentiments, facts, incidents, etc., which are not expression itself, or parts of expression that lack creativity," it does not constitute an adaptation (and by extension, infringement). This decision firmly established that the similarity analysis must focus on the shared creative expression. In the Esashi Oiwake case, the defendant broadcaster's narration described the Esashi Oiwake folk song festival in a sequence similar to the plaintiff's non-fiction work (e.g., past prosperity from herring fishing, present decline, the festival as an annual highlight). The lower courts found infringement. However, the Supreme Court overturned this, reasoning that even if the plaintiff's perception or idea about the festival's significance was unique, the idea itself is not protected expression. Since the actual wording and specific expressions used in the narration differed from the plaintiff's work, there was no infringement, despite the shared underlying theme and sequence of presenting information.

Analytical Frameworks for Assessing Similarity

To systematically determine if there is a commonality of creative expression, Japanese courts, particularly in more recent years, have increasingly utilized or referred to concepts similar to those found in other jurisdictions, such as the "filtration test."

1. The "Two-Step Test" vs. The "Filtration Test" (濾過テスト - Roka Tesuto):
   • Two-Step Test (二段階テスト - nidankai tesuto): This traditional approach first examines the plaintiff's work to identify its creative, protectable elements, and then compares these elements with the defendant's work to see if they have been reproduced.
   • Filtration Test (濾過テスト - roka tesuto): This method, which gained prominence after the Esashi Oiwake case, involves first identifying all elements common to both the plaintiff's and defendant's works. Then, unprotectable elements—such as ideas, facts, public domain material, scenes à faire (standard or indispensable elements for a particular genre), and unoriginal components—are "filtered out." If, after this filtration, a substantial similarity remains in the protected creative expression, infringement may be found. This approach is considered more efficient and less prone to mistakenly finding similarity based on unprotectable elements.
2. Qualitative vs. Quantitative Similarity: The assessment of similarity is not purely quantitative (i.e., how much was copied). The qualitative significance of the copied portion is also crucial. Copying a small but highly distinctive and central part of the plaintiff's creative expression can be more significant than copying a larger amount of less original material.
3. Whole Work vs. Part Comparison (全体比較か部分比較か - zentai hikaku ka bubun hikaku ka): Infringement can be found even if the copied creative expression constitutes only a part of the defendant's overall work, or only a part of the plaintiff's work, as long as what was taken is a qualitatively and quantitatively substantial part of the plaintiff's protected expression. The PDF commentary notes that if the plaintiff's creative expression is reproduced, the presence of additional, different material in the defendant's work does not excuse the infringement. The Right to Sunshine (日照権 - Nisshōken) case (Tokyo District Court, June 21, 1978) is cited as an example where even if the pirated part was only 2 pages out of the defendant's 217-page book, it was sufficient for infringement.

The Lingering Debate: "Direct Perception of Essential Features"

Despite the clarity provided by the Esashi Oiwake decision on the "commonality of creative expression," the judgment also retained language about "direct perception of the essential features of the expression format" from the earlier Parody case. This has led to ongoing academic discussion about whether "direct perception of essential features" constitutes a distinct, additional requirement for similarity, or if it is now essentially synonymous with or incorporated into the "commonality of creative expression" analysis.

• Unitary View (Creative Expression is Key): A prominent view is that "essential features" simply refers to the "creative expression" itself, and the Esashi Oiwake court used the older phrasing for jurisprudential continuity. Under this view, the analysis primarily focuses on whether creative expression is shared.
• Dual Standard View (Separate "Direct Perception" Test): Another perspective, gaining some traction, argues that "direct perception of essential features" acts as an additional, potentially higher, hurdle. This might be invoked in specific contexts like parody or incidental inclusion, where even if some creative expression is technically shared, it might be so transformed or "faded" (色あせ基準説 - iroase kijun-setsu) within the new work that its original "essential features" are no longer "directly perceptible," thus negating infringement. This could also involve a "correlation theory of creativity" (創作性の相関関係理論 - sōsakusei no sōkan kankei riron), where the new creative contributions in the defendant's work are weighed against the copied elements. However, such approaches can introduce uncertainty.

Specific Contexts for Similarity Analysis

• Sequels (続編 - zokuhen):
  • Novels: Creating a sequel to a novel that uses the same characters and general setting but tells a new story with different specific plot points and dialogue typically does not infringe the copyright in the original novel's expression. This is because abstract characters and settings are generally considered ideas rather than protected expression. The Supreme Court in the Popeye case (July 17, 1997) stated that a "character" as an abstract concept, separate from its concrete expression in a specific manga installment, is not itself a copyrighted work.
  • Manga and Visual Works: In contrast, creating a sequel to a manga or other visual work that reproduces the specific artistic depiction (e.g., the drawings) of characters is more likely to constitute copyright infringement, as this involves copying protected artistic expression.
• The Candy Candy Doctrine (Supreme Court, October 25, 2001): This highly debated decision concerned a manga created through the collaboration of a storyteller (original author) and an artist. The court held that the original author (storyteller) could assert copyright infringement claims even against the artist's later use of character depictions that the artist herself had visually created for the manga, if those depictions were based on the original story. The reasoning, based on Article 28 of the Copyright Act (rights of the author of the original work in the exploitation of a derivative work), effectively allows the author of an original underlying work to control uses of new creative expression added by the author of the derivative work, if that new expression is still considered part of the overall "derivative work." This ruling has been heavily criticized by legal scholars for potentially granting the original author rights beyond their own creative contribution and unduly restricting the derivative work's author. The concern is that it could extend the original author's monopoly to aspects they did not create, especially if the derivative work significantly transforms or adds to the original.

Comparing Japanese and U.S. Approaches to Infringement Elements

While the foundational principles of copyright infringement share common ground internationally, there are differences in emphasis and application between Japanese and U.S. law.

• Reliance (Ikyo) vs. Copying (with Access and Probative Similarity): The Japanese "reliance" requirement is conceptually similar to the U.S. requirement to prove "copying." In the U.S., copying is often proven circumstantially through evidence of the defendant's "access" to the copyrighted work and "probative similarity" between the works (which can give rise to an inference of copying). Japan also uses access and similarity to infer reliance, but the legal terminology and emphasis might differ slightly.
• Similarity (Ruiji-sei) vs. Substantial Similarity & The Filtration Test: The Japanese concept of actionable similarity focusing on "commonality of creative expression" and the use of a "filtration test" have strong parallels with the U.S. doctrine of "substantial similarity." The U.S. also employs various tests, including filtration (e.g., the abstraction-filtration-comparison test prominent in software cases), to separate protectable expression from unprotectable ideas and elements. The core objective in both systems is to ensure that liability is based on the copying of protected original expression.

Conclusion

Determining copyright infringement in Japan hinges significantly on establishing both reliance (copying) and the requisite similarity between the defendant's work and the plaintiff's protected creative expression. The Japanese legal framework, particularly through court precedents like Esashi Oiwake, emphasizes that mere taking of ideas or common elements is insufficient; it is the reproduction of the author's original, creative contributions that triggers liability. For businesses and creators, a thorough understanding of how Japanese law defines and analyzes these elements—especially the focus on "creative expression" and the practical application of tools like the filtration test—is indispensable for navigating copyright issues and mitigating infringement risks in the Japanese market.