[mesmark]

Chris - There's a lot of research that suggests problems with L1 literacy provide greater problems with L2. It's often recommended, with children, to have the family support L1 literacy at home if say the child has immigrated to an English speaking country.

I think the same could be applied to adults learning a second language. That student(s) might need to seek litteracy assistance for Japanese as well as attend English lessons.

Aside:
I have a student who is almost incomprehensible (for me) in L1 due to his language usage and what appears to be a trend in him to leave all thoughts unfinished. He also explains things with single words instead of articulating them with full(er) thoughts. Those traits prove devastating to his English (low context language) performance.

His reading and writing are fine in both languages though ...