TERUAKI MASUMOTO is a 48-year-old tuna department manager at the Tohto Suisan Company in Tokyo, Japan. He’s soft-spoken and was a bit weary-eyed from traveling when I met him in Washington last week. For more than 20 years, Masumoto has had to live without knowing what happened to his sister the day she vanished, August 12, 1978: “I was a 22-year-old student and my sister Rumiko was 24 and working as a clerk,” he tells me through a translator. “It was a holiday so I was home from school and saw my sister off–she was going out with her boyfriend Shuichi to the beach on the Fukiage Coast, known for its beautiful sunsets. And that was the last time I saw her.” Masumoto knew something was wrong when she didn’t come home that night. “Before that night, she never stayed out late. It was very unlike her.”

The next day, Shuichi’s car was found in a parking lot near the beach. It was locked and Rumiko’s handbag, a wallet with money, and a camera were still inside. “Because they were dating, many people thought they had eloped. But they had been going out for only two or three months and she hadn’t even met his parents. We later found one of Shuichi’s sandals near the beach path and thought it could’ve been a crime, but police were doubtful. So we thought maybe it was an accident. It got so crazy some even thought they might have been abducted by a UFO. For those first few years, we didn’t have any answers.”