Murder Case: Lover Swap(1982)

Murder Case: Lover Swap is a Japanese thriller series that begins when a couple's winter getaway takes a sinister turn. Yoshiko Konno and her fiancé Yoichi Itokawa become stranded at a remote mountain cottage after their car gets lost in a blizzard. They rent a room and meet several other guests gathered by the fireplace. That night, Yoshiko wakes to a woman's voice from the adjacent room and ventures out to investigate, only to discover that nothing at the isolated lodge is quite what it seems. As secrets unravel among the trapped guests, the evening spirals into a dangerous game where trust becomes a liability and everyone becomes a suspect.