In Mr. Hosoda’s case, growing up as a girl named Mika in Iruma she never met anyone who was transgender and did not even know it was possible to transition from female to male.

All she knew was that she did not feel like a girl. She hated being forced to wear a skirt as part of her uniform in high school. When it came time for her coming-of-age ceremony at age 20, she balked at having to wear a feminine kimono.

Through an internet connection, she met a man who had transitioned from a woman, opening her eyes to the possibility of another life path. This mentor encouraged her to come out to her parents.

Anxious about how they would respond, she wrote a letter and handed it to her mother in the parking lot of a supermarket. She feared that if she handed over the letter at home, she would just run to her room rather than face her mother’s reaction.

Mr. Hosoda, who was then studying to be a medical technician, recalled that after his mother read the letter, the first words out of her mouth were “I’m so sorry.” She was devastated to learn that her daughter had been suffering in silence for so long, and wanted to offer her child her full support as daughter transitioned to son.

In 2014, Mr. Hosoda underwent sexual reassignment surgery, which allowed him to convert his gender on his official family register.