Mutsugorō, a researcher studying wild bears, moves his family to a remote, uninhabited island near Hokkaido to observe the local bear population. Poachers operating nearby pose a key challenge to his research. During fieldwork, he discovers an orphaned bear cub, likely orphaned by poachers, and takes in the cub named Donbe. Raising Donbe as part of their family, they incorporate the bear into daily life while continuing their scientific mission. The persistent threat from poachers endangers their research and the safety of both family and bear. Despite this, Mutsugorō remains dedicated to studying bear behavior and protecting Donbe.