I’m a therapist who works with a lot of trans kids. The recommendations in this thread are great!

Since you specifically requested books, this is my go-to recommendation for parents of my trans clients: https://www.simonandschuster.com/books/The-Transgender-Child-Revised-Updated-Edition/Stephanie-Brill/9781627783248 . If you buy and read one book, this is the one I’d choose.

I’m pretty sure that’s the joke.

Just as an FYI: although laws are strict about US-based therapists practicing only in states where they are licensed, there are no laws regulating international practice of psychotherapy. If the people you’re talking about have a hard time in Japanese, they may be able to to find a telehealth therapist in their country of origin who speaks their native language and is embedded in their native culture. You have to deal with timezone shenanigans, but it beats going without. Something to consider.