That is different from going around and just interacting with them, which I found smooth and polite.
If you think that interacting eith japanese at work or shops or restaurants is the same as becoming part of them, well, that is ok, you seem to live there. I think it is more difficult than in other countrues and by this I am not meaning they are bad.
For example, far fewer japanese speak english than other developed countries, which is a trait of ehat they care about.
Also, when working or interacting with japanese myself, I found they follow rules really strictly compared to the "flexibility mindset" that westerners tend to have when solving problems.
They will not go and correct their bosses if they see mistakes because "they will notice themselves". So there is a lot of room to make innocent mistakes when interacting with them and many, face it, are not even that interested beyond a trivial and polite conversation and I am not meaning bad. Every culture has their priorities and taste.
My point was specifically about decoupling culture from language. And notably you didn't clarify about the Romanian who I guess must have spoke Spanish.
Sorry but there are many eastern countries that are considered "developed" while the English speaking population is nothing compared to Western countries like in the Europe. Of course I wish they taught if better to open global opportunities but that doesn't mean anything in terms of culture. It's a language issue and luckily AI is much better at dealing with them than culture.
Said in another way: they will just tell you the positive stuff and will discard negative things. Why? Because for them "projecting negativity" is something plain bad and wrong. This is the reason, for example, why it is almost impossiboe to see a japanese crying in public. That is projecting negativity. They will not go and tell you: "man, how did you comb today you look crazy", even if it is what they are thinking. And like this, millions of things. So maybe you think they are polite or even they like you just bc u dnt get any of this, but observe further: they put distance, they do not make you into their groups except for really formal appointments (business, work), etc. No, it is not easy to get integrated in Japan. It is just not easy.
That they are amazingly polite when dealing with you does not mean you are fully integrated at all.
It means they are polite. Nothing else. If you do not believe me, try to make yourself the person in a group surrounded by japanese. It is very likely, to say it plainly, that you are not just accepted as one more in their circles. For business yes, for close friendship, I doubt it in most cases though this varies a bit in bigger places.
It is really tough.
I don't need to try to do this, close friendships with Japanese people and integration in social circles where I'm the only non-Japanese has not been hard. The strategy is just not to have your own preconception of outsiderness.
I see many that complain about difficulty integrating similar to your comments, blaming it on something about the Japanese people. But they themselves didn't make the effort to learn the language or make friends in a more casual way, so it just seems like a responsibility deflection. Maybe this is what you mean by it being really tough, but it seems a pretty normal amount of effort when immigrating to me. Pushing this narrative that it's really hard (some of the language even made it sound like implying impossible) doesn't help make it easier since then people get this preconception of being an outsider, and yes that will do a good job of preventing integration.