O-gata Ketsueki Stewardess Satsujin Jiken(1985)

A flight attendant named Fubuki Omachi suddenly disappeared after a flight one day. Her younger sister, Himemi Omachi, her only surviving relative, had been searching for her ever since. One night, a year after her disappearance, Himemi had a dream in which her sister was beckoning to her from a creepy swamp. The swamp looked familiar to Himemi, and when she went there, she discovered a plastic bag floating on the water’s surface. The bag contained a skull, and after reconstructing the face, she realized it was her sister’s. Himemi believed the person who killed her sister worked at the airline where her sister had been employed, so after studying intensively, she joined the company as a flight attendant.

Who was the killer who murdered Himemi’s older sister…?

(Source: Kaiki Manga no Anagura, translated)