Our friend patio11 wrote a bit about it here:
http://www.kalzumeus.com/2014/11/07/doing-business-in-japan/
Re:Tokyo vs. the Bay Area
by unsignedint on Sunday August 30, 2015 @02:19PM
(#10144076)
One detail missing from their overtime situation is a lot of companies do not practice interval between work hours. This basically means you can be forced to work until 5AM and then expected to show up 9AM in the morning.
There seems to be some talk about the regulatory amendment to fix this, but considering current "service overtime" already crossing legal limit, I don't know how effective that will be.
However, according to my Japanese teacher many people in Japan have to work until 8pm or later on a regular basis, and sometimes overtime. Does anyone have those kind of experience in Tokyo's tech industry?