TOKYO (AP) — A senior member of yakuza was arrested for allegedly stealing Pokemon cards near Tokyo in April, a case seen as an example of Japanese organized crime groups struggling with declining membership.

Police agents who were busy dealing with thousands of yakuza members just a few years ago have noticed something new: unorganized and loosely connected groups they believe are behind a series of crimes once dominated by yakuza.

Police call them “tokuryu,” anonymous gangsters and tech-savvy young people hired for specific jobs. They often cooperate with yakuza, obscuring the boundary between them and making police investigations more difficult, experts and authorities say.

The Tokyo metropolitan police are currently investigating six suspects in their 20s and 30s, most of them without connections to one another, who are believed to have been hired on social media to kill, transport and burn the bodies of an older couple at a riverbank of Nasu, 200 kilometers (124 miles) northeast of Tokyo.