“It was thanks to Kumamon that yuru-chara became a national phenomenon,” said Shuichiro Nishi, the creative force behind the competition.

When the charmingly plump black bear with rosy red cheeks won the event, the country was still reeling from the catastrophic tsunami and nuclear disaster that had struck northern Japan months earlier. People were “clamoring” for a sense of national connection, Mr. Nishi said.

Kumamon moved mountains of merchandise and drove up tourism. Hit mascots can also lift tax revenue thanks to a program, introduced in 2008, that allows citizens to direct a portion of their income taxes to the locality of their choice.

Inspired by Kumamon’s success, local governments rushed to cash in. As the characters became fixtures on national airwaves, Mr. Inuyama said, the media “tricked people into thinking yuru-chara were making money,” and local governments “went along for the ride.”

More and more, though, it looks like the end of the road. The number of characters in this November’s Grand Prix, held in Nagano, was down a third from the peak of about 1,700 in 2015. Many of the entrants did not even bother to show up. And officials, seeing the writing on the wall, announced that the 2020 contest would be the last.

Misabo’s handlers, however, were not about to give up.

The mayor had given them one year to show that the character was worth the tens of thousands of dollars that taxpayers had spent on him.