Police found the body of a woman on Friday in a forest in Akita Prefecture. Investigators said she appeared to have been mauled by a bear.
The bodies of 3 men were found in the same area over a 3-week period. All 4 had been collecting bamboo shoots and other edible plants.
Local officials in the northeast say the number of bear sightings is up this year by more than 50 percent compared to last year.
One expert says more bears were probably born this season because of bumper crop of beechnuts last autumn. Female bears feed on the nuts.
"Both bears and humans go into the mountains to search for edible wild plants. And both are likely to panic if they suddenly encounter each other. Mother bears instinctively use all their strength to protect their cubs from anyone who might pose a threat," says Teruki Oka, who is with the Forestry and Forest Products Research Institute.
So why do local people enter the forest despite the threat?
Kenichi Goto says many are lured by a seasonal bamboo shoot called Nemagari-dake. The bamboo shoot is popular for its taste, and it can be sold. Unfortunately, bears love the plant too.
Goto ran into a bear 2 years ago. He said the animal tore up his backpack. Since then he has been a lot more careful.
"I make sure not to go into the woods by myself. I also stay clear of places where bears have been spotted," he says.
In the mountains where the 4 mauled bodies were found, city officials asked hunters to track and kill the bear.
Nobuo Kurosawa, a hunter, made a sign that a bear had been shot.
"The bear came out of that bush and stood up. I saw the white crescent mark on its chest. There are still a lot of bears around here," said Kurosawa said.
It was a female, about 1.5 meters tall. But it's not clear if she was the attacker.
It's not just the woods that can be dangerous. Experts say bears have been known to stray far and wide, including into town.
They warn that one could be lurking closer to home than you think.