In interviews and public appearances, Yusuke Narita, an assistant professor of economics at Yale, has taken on the question of how to deal with the burdens of Japan's rapidly aging society.

"I feel like the only solution is pretty clear," he said during one online news program in late 2021. "In the end, isn't it mass suicide and mass 'seppuku' of the elderly?" Seppuku is an act of ritual disembowelment that was a code among dishonored samurai in the 19th century.

Last year, when asked by a school-age boy to elaborate on his mass seppuku theories, Dr. Narita graphically described to a group of assembled students a scene from "Midsommar," a 2019 horror film in which a Swedish cult sends one of its oldest members to commit suicide by jumping off a cliff.

"Whether that's a good thing or not, that's a more difficult question to answer," Dr. Narita told the questioner as he assiduously scribbled notes. "So if you think that's good, then maybe you can work hard toward creating a society like that."