When someone leaves work in Japan, colleagues will often say otsukaresama desu rather than goodbye. The same phrase may be used when coworkers pass each other in the office, call or message one another, greet someone returning from outside the office, or finish even a short meeting.
It does not always mean that the speaker is genuinely concerned about how tired the other person is. In the workplace, otsukaresama desu has become something close to an all-purpose expression. It can serve as a greeting, mark the end of an activity, or acknowledge that someone has been working.
It is also flexible about status. A manager can say it to an employee, an employee can say it to a manager, and coworkers can say it to one another. Japanese speakers therefore use it without having to think carefully about who ranks above whom. Being told otsukaresama desu does not normally make someone think, “They must believe I look exhausted.”
Gokurousama also recognizes someone’s work, but it cannot be used as freely. It carries the tone of someone in a higher position acknowledging work done by someone below them. A company president may naturally say it to an employee, and a manager may say it to a subordinate. When used in that direction, it can sound warm and appreciative rather than arrogant.
The problem appears when the direction is reversed. If an employee says gokurousama desu to a manager, it can sound quite disrespectful. Adding the polite ending desu makes the sentence grammatically polite, but it does not remove the hierarchy built into gokurousama. The employee may sound as though they are speaking from a higher position and assessing the manager’s work.
Even between coworkers of equal status, gokurousama can sound slightly patronizing. The words are meant as praise, but the speaker may seem to be placing themselves in the position of the person giving approval.
A foreign learner who makes this mistake will often be forgiven. Japanese coworkers may assume that the person has not yet learned the hierarchy built into the phrase. The same mistake made by a Japanese employee is more likely to be taken seriously, because they are expected to understand how it sounds.
When in doubt, use otsukaresama desu. It works for someone who has finished a task, someone you are about to speak to, and someone leaving for the day. In most Japanese workplaces, it is far safer and more natural than trying to decide whether gokurousama fits.