In his early 70s, Koji Uchida began to vanish.

The first time, the police found him sitting in front of a vending machine 17 miles (27 kilometers) from home. He began to go missing regularly, once wandering for two days before turning up at a stranger’s apartment, hungry and barely able to remember his name, his mind clouded by dementia.

At a loss for what to do, his family asked the local government to put Uchida under digital surveillance.