As you know, Japanese are love to work hard and spend most of their time in their office. When it is time to leave you will have to follow some customs.
When you leave for the day
+ Tidy up your place
+ Move your chair closer to the desk
+ Do not forget to say "O saki ni shitsurei shimasu" to others who are working late
NOTE: Other employees who are working late will say "O tsukare sama desu"
+ When other employees leave before you, say "O tsukare sama desu"