Usui told his family he was going hiking on Mount Arafune that morning and would return to his home in Kasukabe, Saitama Prefecture, by evening, the police said. His family reported him missing the next day.
The Japan Times online reported that the Saitama, Gunma and Nagano prefectural police forces have been conducting a joint search for him ever since.
Usui started drawing "Crayon Shinchan," the story of feisty kindergartner Shinnosuke Nohara and his family in Kasukabe, in a comic book published by Futabasha Publishers Ltd. in 1990. The popular cartoon series was adapted for both television and film.
The city of Kasukabe issued a special residence card to the Nohara family to commemorate the 50th anniversary of the municipality, and has also been using Shinchan as a mascot for its child-rearing campaign since April.