Recently I had a ceiling fan installed in my home in San Diego. Two electricians came to perform the installation cheerfully ran the wiring, talking among themselves in a foreign language as they worked, and cunning linguist that I am, I happened to notice they were switching between English and their native language (which turned out to be Armenian, as they’d come over as refugees when they were very young). Shifting between two languages when speaking with someone who also understands both is known as “code switching,” and it’s a natural part of the communication process. Japanese-English bilinguals do it too, cherry-picking English words that capture a certain emotion here, then using a bit of Japanese slang there to add flavor. If nothing else, Japanese-bilingual foreigners will generally express all numbers in Japanese, due to the fact that the Chinese-Japanese numeric system is based on 10,000, whereas we use a system based on 1,000. Converting “10 mahn” (10 units of 10,000, aka 100,000) into English on the fly is more work than my brain can usually handle.
Hope everyone is having a Very Touhou Summer so far!