‘Johatsu” means evaporation in Japanese, and is used to refer to those people who choose to disappear, severing all ties with their past lives and their families. It became a phenomenon in Japan in the 1960s, and intensified during the 1990s as the country struggled with a debt crisis. While some plot their departures on their own, others call on the services of “night movers”: companies that help people vanish without trace.

Following the owner of one such business named Saita, Andreas Hartmann’s and Arata Mori’s poignant documentary surveys the circumstances that drive people to desperate measures. Unfolding like a suspense thriller, the opening sees a man hurriedly get inside Saita’s van, his voice trembling with fear. Unable to cope with a possessive partner, he finally manages to flee. Interviews with Saita’s other clients reveal that, besides financial catastrophes, domestic abuse is often a catalyst for escape. At the same time, the reasons for a disappearance are not always clear-cut, and the film not only lends an ear to the “evaporated” but is also sympathetic to the abandoned, who are left with gnawing questions and no answers.

The juxtaposition of intimate interviews and static shots of nondescript Japanese towns adds another element of melancholy. These compositions show how johatsu is not just an individual decision but a manifestation of larger societal issues.

Interestingly, since the subjects only agree to participate on the condition that the film will never be screened in Japan, their new homes and identities are carefully obscured. But in an age when a film can travel far and wide virtually, it remains to be seen whether such measures are enough to protect their anonymity.

• Johatsu is at Bertha DocHouse, London, from 28 February.