Some people say that when they use ToyCamera / OldCamera their navigation is Japanese. I reserched the issue and find the problem. It will potentially happen with NON-English users.
It is language priority issue of iPhone. In your iPhone, if Japanese is treated as higher priority than English, it displays Japanese.
To solve problem,
1: Opne iPhone’s setting panel.
2: Find the language setting / its in the General setting.
3: Check language order, I think Japanese must be placed above the English.
4: Select English as your first language.
5: After select your mother language as your first language.
6: Now English has higher priority than Japanse.
It should be work like a charm :-)