His affairs with men included a ten-year relationship with Kunihiko Hashimoto, a Tokyo insurance employee. The two met when the New York Philharmonic was performing in Tokyo. Hashimoto went backstage and they ended up spending the night together. It was a long distance affair, but according to letters, they both cared about each other deeply. "Dearest Lenny: Letters from Japan and the Making of the World Maestro" by Mari Yoshihara (Oxford University Press, 2019) goes into detail about their letters and relationship including interviews with Hashimoto. The book also includes other letters Bernstein received from Japanese fans.