Earlier quoted context omitted.
Telling someone “just speak Japanese and blend in!” is sort of an absurd suggestion. That is impossible if you’re not East Asian and even if you are, it would take years of study.
Being East Asian doesn't make you blend in (visually). Japanese people look different to Korean and Chinese people.
Clothing and makeup is a better giveaway than facial features or skin tone, but even that is becoming harder with K-pop creating a pan-Asian style to aspire to.