High-profile Japanese anime voice actor Kenjiro Tsuda has taken TikTok to court over videos he says feature an artificial intelligence (AI) clone of his “lustrous” baritone, with a verdict due on Wednesday.

The lawsuit filed by Tsuda, known for his starring roles in mega-franchises including ‘Jujutsu Kaisen’, ‘Chainsaw Man’ and ‘Yu-Gi-Oh!’, is believed to be the country’s first seeking to defend an individual’s vocal identity against AI-generated copies.

Tsuda is demanding TikTok remove a slew of videos narrated by a distinctively “deep” and “lustrous” voice that the 55-year-old says can only be his.

The platform, however, argues it is a “generic male voice” whose perceived similarity to Tsuda’s is subjective at best, according to court records accessed by AFP.

AI imitation is a growing concern among performers worldwide, and the threat has roiled Japan’s storied animation industry, whose voice actors are sometimes worshipped as much as their characters by fans.

An actor’s voice “is the result of years of rigorous training and apprenticeship” to hone talent, Yuko Sasaki, executive director of the Japan Actors Union, told AFP.

“It’s something we spend lots of time and money perfecting,” said Sasaki, a fellow voice actor, adding that “we support Tsuda wholeheartedly”.

The court should “acknowledge that ownership of a voice is a fundamental right”, she said.

An anonymous account, whose picture resembled Kento Nanami, a ‘Jujutsu Kaisen’ character dubbed by Tsuda, posted the videos in question.

They combined images and seemingly AI-generated speech about urban legends, occult phenomena and conspiracy theories.

The account at one point boasted more than 200,000 subscribers and would have brought in upwards of 500,000 yen ($3,200) in monthly revenue, the legal complaint argued.

‘Sordid content’

The account, whose posts mostly lacked original substance, “only gained popularity because its dubious, sordid content was narrated by the attractive voice of a popular actor”, Tsuda’s legal team said, according to the court records.

This infringes Tsuda’s so-called publicity rights — the ability to control and profit from the use of aspects of one’s identity — his attorneys said.

Although the account itself is no longer viewable on the platform, the Tokyo District Court will rule on whether TikTok was responsible for deleting the posts.

Parallel to the lawsuit, Sasaki and other Japanese voice actors have launched a campaign, called “No More”, against using generative AI to mimic performers without permission.

“Our industry can be crushed” if a court win for TikTok triggers “unbridled” AI voice cloning on social media, actor Bin Shimada told AFP.

That could cause younger actors to “lose hope”, said Shimada, who is part of the campaign group.

It is also fast becoming a global issue.

“In many countries, copyright and data protection laws are not being adequately adapted” to protect performers from AI clones, the International Federation of Actors said last year.

ChatGPT maker OpenAI was forced to apologise in 2024 to star Scarlett Johansson over a synthetic voice that sounded like her, released after she declined to work with OpenAI on the project.

International interest

While no law explicitly enshrines a person’s voice in Japan, the justice ministry published legally non-binding guidelines last month clarifying its protection under existing rights.

As “the symbol of one’s personality”, voice is subject to “publicity rights” and “rights to prevent unauthorised use of one’s portrait and likeness”, the ministry said.

But it remains to be seen whether and how the guidelines will influence Wednesday’s court decision on Tsuda’s case.

TikTok has questioned the actor’s “national fame”, rejecting his accusations that the account was free-riding on a well-known brand in a violation of Japan’s unfair competition prevention laws.

As a platform, all it did was “host a forum where users could post creative and ingenious content within the scope of free speech”, it told the court.

It is “very unlikely” that Tsuda’s voice will be outright denied publicity rights, Tatsuhiro Ueno, a professor of intellectual property studies at Waseda University, told AFP.

Given the actor’s ‘Jujutsu Kaisen’ role as a stoic, elite sorcerer that made his voice “highly recognisable in Europe”, Ueno believes the verdict “will garner a lot of international interest”.

Veteran voice actor Michihiro Ikemizu, 83, also expressed solidarity with Tsuda — but said that AI, however sophisticated it gets, will never outperform human actors.

“You need to constantly feel and adapt while performing your role. That’s something AI can never do,” Ikemizu told AFP.

“That’s our only weapon.”