Unwritten social rules are some guidelines that anyone in the society is advised to follow to feel comfortable living there. Generally speaking, Japanese are quite generous to anyone who was born outside Japan, and not expecting them to act as it is. The rule, or custom, does not apply to you but it is still good to know.
There are hundreds of social codes that outsiders would never understand in the corporate environment. From where to sit in the taxi, where to stand in the lift, escalator.
Here are some extreme examples of how people act in the culture
The Order of email addresses
In the average corporate culture, it is easy to see how to display your respect to your senior if in a tangible world. The seating arrangements are quite obvious.
Some people even care about the address line, the order of email addresses, which is not really visible unless you really check it.
When sending an email to multiple recipients, one would not want to place a senior person after his/her junior person. It should start with CEO, followed by COO, Senior Director, and Manager, so on.
Then the question is when you have the person with the same title. One would then have to think of the length of employment at the company, birth date, etc.
The Angle of Seals
This is something I have never seen in my life up until recently, and I found this is quite insane.
The left seal is the one for the senior, and the right one is of his subordinate. When placing the seal, often used in the document for approval, the subordinate is to have some angle to bow to his senior.
These above are extreme cases which would not apply the majority of people but just for your knowledge.