This is mainly second-hand information. I haven't worked at a Japanese company, the closest I've gotten was interviews and a sort of off the record job offer. I have lived in the country for 1 year though, so I definitely saw the actual hours friends were at work or busy because of work.

1. Japanese business culture sees labor laws as guidelines.

2. Being overworked (meaning enduring or working extra hours) is seen as a "good" thing.

3. Doing anything to sabotage the team effort (including working fewer hours, not being available, not asking to help others) is seen as the worst thing you could do.

4. Being granted a week off by your company is seen as generous (even though you may be allocated 2 or more weeks a year). The corollary to this is not taking your allocated vacation hours is seen as a good thing.

5. You don't miss work due to a cold, you put on a mask and show up anyway.

6. Punctuality is in some ways more important than doing the actual job. This is why people go through great efforts to jam into a single train in order to not be late by even 5 minutes.

7. Apologies are expected, more than reasons or explanations. The message your superior wants to hear isn't that you screwed up, it is that you are inferior and have no excuse and he is superior to you (hence an apology). This is a legacy of Japan's feudal days; Japanese large corporations are essentially the transformation of what used to be feudal powers.

8. Confrontation is avoided at great lengths. This is why Japanese have a hard time of saying "no". This implies that if your boss asks for work to be done, you will undoubtedly agree without complaint.

9. Women are paid significantly less than men, but the trade off is a woman can quit her job to rear children and not be "penalized" from a social standpoint. Men get paid more than women but Japanese culture expects that the man of the family will pay for his wife and children in full through retirement even if the woman doesn't work a single day.

10. Since men are the de facto breadwinner, and women often don't work to take care of the household/children, men are expected (even by their own families) to work longer hours in order to advance the entire family. It is not uncommon for the father of a family to live/work in a city 2-3 hours away from where his family resides.

11. "Black" company (in Japanese) is a term that refers to businesses that have mandatory overtime (12+ hour days). I guesstimate roughly half of all companies in Japan are Black companies.

12. Companies often have "Nomikai" (drinking parties). They are not mandatory per se, but like everything in Japan, social pressure is often used to force people to attend. This is considered a work function even though no actual work takes place.

13. Most employees in Japan are part of "sales". This doesn't imply selling a product, rather it means wining and dining to the customer (Business to Business). This includes things like taking the customer on dinners, karaoke, golf, etc all "on the house". Failure to do this mean strain on the customer relationship. Strain on the relationship implies loss of business.

14. There's a "right" way of doing everything. Japan is a society that values process and manners. For example when you, a Japanese national, go on an interview, and must enter an interview room, you first knock exactly 3 times, yell "excuse me", wait for an invitation, open the door, yell again "pardon me", then enter the room, promptly close the door, wait to be invited again to take a seat, then proceed to take the seat. Failure to do this correctly exactly as listed looks bad.

15. Japanese (the language) continues to require honorific/humble language in addition to polite language. In school, children must address students senior to themselves using polite language. In the workplace, employees must be able to address superiors and customers using honorific/humble language (a step above polite language, imagine talking to a king in the old days with English). Distant acquaintances and strangers must also be addressed with at a minimum polite language. Casual language is reserved for friends and family only. To be fair, this isn't just unique to Japan but is common in many East-Asian and nearby cultures.

16. If you want to avoid this hellish landscape and remain in Japan and still be respected, you do have one and only one option. Do well on your college entrance exams in high school, get into the top tier schools, then apply to the top companies and highly desired positions. This will spare you of regular mandatory overtime during your adult life, allow you to have better than average salary, and still be highly respected in society despite only working may an average 10 hours a weekday. Doing something else (like going abroad) is not seen as the "normal" way. Not being normal is not good. The only exceptions are English teachers, translators, and obviously affluent families (that would have been fine anyway). University students can also get away with study abroad, assuming they don't go more than a year and join the rest of their peers in the same job hunting style at the end of it. But these students may have already accepted that they are unlikely to land a good job so study abroad is seen as a way to delay the inevitable.

17. More and more Japanese are slowly just beginning to say "fuck it". This is leading to interesting subcultures. For example the term called "freeters" (shortening of English free-timers) is a culture of young Japanese that refuse to work standard salary jobs and instead work multiple part time jobs often taking breaks in employment to enjoy free time. More 20s and 30s Japanese are taking advantage of working holiday visa arrangements with other countries as an attempt to expatriate. More and more Japanese are negotiating or purposely deciding to only take jobs where they are allowed a fixed number of hours (often the cost is a reduction in pay or a not so great work assignment). But these groups are still very much the minority and there are definite sacrifices these people have made (or they're just mentally crazy) in the eyes of the typical Japanese.