WHY are the Japanese couples in Kohei Yoshiyuki’s photographs having sex outdoors? Was 1970s Tokyo so crowded, its apartments so small, that they were forced to seek privacy in public parks at night? And what about those peeping toms? Are the couples as oblivious as they seem to the gawkers trespassing on their nocturnal intimacy?

If the social phenomena captured in these photographs seem distinctly linked to Japanese culture, Mr. Yoshiyuki’s images of voyeurs reverberate well beyond it. Viewing his pictures means that you too are looking at activities not meant to be seen. We line up right behind the photographer, surreptitiously watching the peeping toms who are secretly watching the couples. Voyeurism is us.

The series, titled “The Park,” is on view at Yossi Milo Gallery in Chelsea, the first time the photographs have been exhibited since 1979, when they were introduced at Komai Gallery in Tokyo. For that show the pictures were blown up to life size, the gallery lights were turned off, and each visitor was given a flashlight. Mr. Yoshiyuki wanted to reconstruct the darkness of the park. “I wanted people to look at the bodies an inch at a time,” he has said.

The oversize prints were destroyed after the show, and the series was published in 1980 as a book, one now difficult to find. Last year Mr. Yoshiyuki made new editions of the prints in several sizes, which have brought renewed interest in his work. Since April images from the series have been acquired by the Museum of Modern Art in New York, the Museum of Contemporary Photography in Chicago, the Museum of Fine Arts in Houston and the San Francisco Museum of Modern Art.