and it’s a fairly common way of asking someone to start dating exclusively.
The vast majority (upwards of 90%, I’d say) hardly have the opportunity to interact with non-Japanese unless they travel overseas.
Surely each individual is unique, and generalizations/stereotypes about an entire culture can’t be made based on a very little number of individuals.
However, from an anthropological perspective, certain cultures tend to practice same rituals due to the culture transmission throughout the years, and even though an individual may have his/her particular characteristics, a community in many cases is fostered and developed to shape a shared mindset that may not always function exactly the same way but definitely in parallel.
If you’ve been Japan for more than 5 seconds and had any interaction with the opposite sex here, you’ll no doubt have already experienced some “Lost in translation” style mishaps from smashing against the language barrier and cultural differences.
Japanese culture is at times pretty much the exact reverse of western culture.