Yes, it is difficult to make friends with Japanese people. There are many reasons behind it but the primary reason is their culture is totally different from the western countries. It is easier to make Japanese friends when you live there from childhood and it becomes difficult when you visit the place for a job, business, or travel purpose and try to make friends with them.
Basically Japanese work for 10-14 hrs, they work hard and give less importance to social life. I would also say Japanese are more introverts and they will have friends with only known persons most of the time. This is the reverse situation in Western societies that they judge introverts as lacking in confidence and character and annoying. Coming from a more extrovert society can make it difficult to make friends here.
So that’s the reason even affecting their personal relationships, and the stats say the marriage rate is declining every year in the country. Online and offline dating services are picking up and in fact, people are slowly accepting it. And I have a dought whether they choose their friends or any other romantic partner for marriage? someone has to do deep research on the matter to understand them better.
In most cases, Language becomes a barrier for foreigners, if you think you can survive by knowing the English language you are wrong because you can find English speaking Japanese people only in urban areas and it is hard to find in rural areas. So if you are planning to live in rural areas it’s better to learn some Japanese language before you go.
The busy schedule was not only a factor in not making friends, but they also wanted to see trust and feel safe with you before making friends. This may be the habit from childhood since most schools teach their students to be careful with strangers and teachers will restrict relationships among co-students, this habit may be the reason which made them continue even after grown-up. Check out the detailed information on facts about Japanese schools.
Some foreigners who stayed for a long time have shared their experience with us, where they said most of the people live alone in their homes and even if someone dies people will come to know only when the smell of the body spreads to the surrounding area and then they will complain to the authorities. Think how much introvert people they are, there may be few cases like this but it gives an idea of how they live.
Even if the Japanese make friends with you, most of them will be less active with you because of their busy work schedules. Sometimes they may hangout a night party or so but the next day they will be a different person and start ignoring you and get involved in their daily routine.