Japanese IT journalist Nobi made a good catch finding new unannounced Japanese fonts in the macOS Sierra developer beta. All seven new fonts, ten if count by font weights, were created by Jiyukobo, the same font studio that created the macOS Japanese system font Hiragino. I hope to interview head designer Torinoumi san about the new fonts before the official macOS Sierra release this fall.
The most interesting thing about these new fonts are the two flavors of the school textbook font Yu Kyokasho that Apple chose to include. Yu Kyokasho is tuned for vertical layout while Yu Kyokasho Yoko is tuned for horizontal layout. Japanese schoolbook fonts have to meet certain design guidelines set by the Ministry of Education, Science and Culture. It will be interesting to see if Apple has any plans to support CJK vertical layout in future versions of Pages and iBooks Author. So far they have not.