During one online news program in late 2021, Yusuke Narita, an assistant professor of economics at Yale, said “I feel like the only solution is pretty clear, . . . In the end, isn’t it mass suicide and mass ‘seppuku’ of the elderly?”

Last year, when asked to elaborate, Dr. Narita graphically described 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.

Now however, Dr. Narita, 37, said that his statements had been “taken out of context,” and that he was mainly addressing a growing effort to push the most senior people out of leadership positions in business and politics — to make room for younger generations.

But critics worry that his comments could summon the kinds of sentiments that led Japan to pass a eugenics law in 1948, under which doctors forcibly sterilized thousands of people with intellectual disabilities, mental illness or genetic disorders. In 2016, a man who believed those with disabilities should be euthanized murdered 19 people at a care home outside Tokyo.