When I first came to Japan, I worked at a company with X hours of overtime included. However, I only remember a couple of occasions where I did overtime, and this was when there were critical issues with the production servers.
I know other people did work more overtime (especially the Japanese employees). I didn't feel my lack of overtime held me back, and I did get a 25% raise after my first year. In the end, it seemed for that company resulted mattered more than a perception of effort.
I've also done consulting work with other startup companies that don't encourage their employees to do overtime, so they do exist.
I also know a lot of companies will have employees work lots of overtime, regardless of seniority. Japanese society puts an emphasis on team over individual. It also is more hierarchical. So unless the company strictly enforces no overtime, things seem to slip towards everyone doing lots, as no one wants to be the first to leave, nor tell their boss they need to push back a deadline because they don't have enough time.
It really depends on the company's culture. If it has a culture of overtime, most people will work overtime regardless of their experience.
You could try taking the attitude that you won't do overtime, despite the company having a culture of it. You won't have your salary docked for not working overtime, but you may be passed up for promotion, face managers who scold you, be given bad assignments, and otherwise be treated badly.
Talking to the company is the best way to go. As you've seen, companies are usually pretty upfront about what the culture of overtime is like. If the prospect of working long hours doesn't match you, I'd suggest you keep looking till you find a company that does match you.