In a Japanese-language thread: one user suggests it's obviously necessary for Mastodon to implement (more than the current level of) age blocking, so you can designate a minimum age for people to read a toot, and this will solve the problem.
That only illustrates how far apart we are: Japanese think the important issue is the age of the *viewer*; Americans think it's about the *apparent age of the imaginary people in the picture*, and if that's too low NOBODY should be allowed to see it.