After dinner on Wednesday, the couple strolled hand-in-hand through the neon-lit streets of eastern Changsha, not far from Mao Zedong’s hometown. Mr. Sun, who works in Internet marketing, is the more outspoken of the two, though he has never had a reputation as a gay activist.

For eight months starting in October 2014, he ran a teahouse in southern Changsha where he gave weekly talks on sexuality and identity. “I wanted to have a little home that was diverse and friendly, and gradually have a world that is diverse and friendly,” he said. During the talks, people would sometimes reveal to others for the first time that they were gay.

Mr. Sun told his family he was gay at age 14, when he was asked by a relative at a dinner for his grandmother’s 70th birthday whether he had a girlfriend. “I like boys,” Mr. Sun recalled saying. He said his father kicked him after they got home, and that he punched his father back.

There followed a “cold war” with his family for seven or eight years, Mr. Sun said. While living with his grandparents, he would bring dates home, and his grandparents would cook them dinner and avoid asking questions.

The thaw did not begin until 2014. That Mother’s Day, Mr. Sun and his mother visited an island in Changsha with a famous statue of a young Mao. “I explained to my mother that being gay is a basic human right,” he said. “It’s internationally recognized. My mother accepted the fact that I’m gay. Since then, my mother has stood by me on this matter.”

The next month, Mr. Sun and Mr. Hu messaged in the chat group. They met in person that day and have not been apart since.

Mr. Hu said his mother now approved of his sexuality, and Mr. Sun plans to meet her for the first time over the Lunar New Year holiday next month. (“I’m nervous — I asked my boyfriend yesterday what gift I should get his mother, and he said, ‘I don’t know, either,’ ” Mr. Sun said.)