Yoshiyuki was a young commercial photographer in Tokyo in the early 1970s when he and a colleague walked through Chuo Park in Shinjuku one night. He noticed a couple on the ground, and then one man creeping toward them, followed by another. “I had my camera, but it was dark,” he told the photographer Nobuyoshi Araki in a 1979 interview for a Japanese publication. Researching the technology in the era before infrared flash units, he found that Kodak made infrared flashbulbs. Yoshiyuki returned to the park, and to two others in Tokyo, through the ’70s. He photographed heterosexual and homosexual couples engaged in sexual activity and the peeping toms who stalked them.