The badly mauled corpse has yet to be identified, but police in Akita prefecture were searching for a 74-year-old woman named as Tsuwa Suzuki, who was reported missing a day earlier, according to local media, which cited police.
Hunters killed a bear just 10 metres from the spot where the woman's remains were discovered in a mountain forest in Kazuno city, in Akita, though it remained unclear if she was killed by that animal, reports said.
A local veterinarian said that as the attacks happened within the same area and in such a short timeframe, the same bear was likely responsible.
"After tasting human flesh, the bear may have learned it can eat them," Takeshi Komatsu told Japan's Kyodo News agency.
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City officials warned locals not to go into the mountains and have set bear traps.
Suzuki, who lives in Towada city in neighbouring Aomori prefecture, is believed to have gone to the area to pick edible wild plants, according to Japan's public broadcaster NHK. A car, thought to be hers, was found close to the scene.
Bear sightings in Japan's rugged north have already surpassed 1,200 this year, almost double that of last year, with some even spotted near residential areas.
He survived for nearly a week after being left at the side of a road in dense mountain woods as punishment for throwing stones at passing cars.