A backlash is growing in Japan over US President Donald Trump's use of popular anime and manga characters in his social media posts.

Upset has been brewing since March, when fans started noticing the president using images of - and in one case depicting himself as - iconic Japanese animation characters like Naruto, Pikachu and Yu-Gi-Oh!.

Almost 20,000 people have now signed an online petition, arguing that he does not share the characters' values and that using them for political purposes could infringe the creators' rights.

Pokémon Company International has condemned Trump's use of its imagery. The BBC has contacted other rights holders and the White House for comment.

The petition calling for Trump and the White House to respect Japanese manga was first launched in March, when a couple of posts caught the attention of some fans.

The official White House X account released videos that combined footage of US military strikes on Iran with clips from Yu-Gi-Oh! and Dragon Ball. A day earlier, the account had published an image with the phrase "Make America Great Again" superimposed on what appears to be a screenshot from the Pokémon Pokopia video game.

The petition was revived after Trump shared a video on Truth Social on Saturday depicting himself as Naruto Uzumaki, the protagonist and namesake of a popular anime and manga series about a young ninja's journey to become the village leader.

Those who signed the petition and other fans online argue the characters convey the importance of courage, friendship, and perseverance to audiences around the world - and Trump's use of them in this way goes against the creators' intentions.

Kanagawa resident Nana Suzuki started the petition. The 34-year-old self-proclaimed anime and manga fanatic told the BBC she felt compelled to take action.

"Kazuki Takahashi, the creator of Yu-Gi-Oh!, passed away after attempting to rescue someone in the ocean," Suzuki said. "It deeply saddened me that his noble spirit, someone who tried to save others and the message of his work, was used in a military context, and that he is no longer alive to speak up for himself."

She wanted to provide a place where people who share the same frustrations could express themselves and show how many people care about respecting Japanese creators and their content. But a small group of fans shrugged aside Trump's use of the images.

One X user found it "hilarious" and thought it would only increase Naruto's international recognition, likening it to the best free publicity in the world. Another user said: "Rather than criticising the clip, I'm proud that Japanese manga has taken the world by storm to the point where the President of America knows Naruto."

Pokémon Company International has said the White House did not have permission to use its imagery.

"We were not involved in its creation or distribution," said Pokémon spokeswoman Sravanthi Dev. "Our mission is to bring the world together, and that mission is not affiliated with any political viewpoint or agenda."