The title says it all already.
I found how to change fonts with
fontspec and lualatex, however I wonder if there is an easy way to mix Latin characters with Japanese characters without explicitly specifying the font all the time. So I can have the classic computer modern for english and another font for Japanese.
xeCJK solves this problem in xelatex, but I could not make it work in lualatex. Maybe the switch could be painless, but maybe there is a solution for lualatex?