Japanese police are cracking down on mischievous linguists who they say cost the country billions of dollars annually in illegally translated copies of manga, video games, and magazines.

Precincts in Kyoto, Yamaguchi, Shizuoka, Mie, and Shimane prefectures have teamed up to arrest five Chinese nationals who are allegedly part of an underground ring that voluntarily translate and post popular Japanese content on Chinese social media. The suspects—all in their 20s—include two students. Accused of translating material between 2015 and 2018, reports translation industry blog Slator, they are said to have copied 15,000 items between them.

Police are still investigating additional possible infringements, and four of the suspects are reportedly cooperating. Among the manga titles known to have been translated and copied is Kimi ni Todoke, or From Me To You, an anime about a kind but creepy-looking girl who scares most people at school. It is (legally) available in Chinese, Italian, French, German, Spanish, Portuguese, and Taiwanese, according to Anime News Network.

Police also said that they had arrested the illegal translator of Yu-Gi-Oh Arc-V!, both the video game and original manga. It’s the story of a 14-year-old who longs to become an entertainment dueler and must face the challenges that come with such aspirations.

Police say the stealthy translators met through online boards. They received either translation or distribution assignments from a single leader, and their content is most often posted on Weibo, the popular Chinese social media platform that is sometimes likened to Twitter. For these unauthorized linguistic efforts, the suspects face up to 10 years in prison, $90,000 worth of fines, and civil suits with possible additional damages.

This isn’t the first time Japanese police have cracked down on Chinese infringers. In 2015, five Chinese nationals were arrested for uploading translated content without permission to the English-language pirate manga website mangapanda, which hosts thousands of works.

Authorities say there are multiple rings of rogue Chinese linguists who volunteer to translate and distribute content. In 2013, the Agency for Cultural Affairs quantified the losses that result from these activities, saying that Chinese copyright infringements of manga, anime, and games alone cost Japan about $38 billion annually.