In Japan, the work culture is that once you're in with a company, you're in for life - you leave university and are hired that spring / hiring period, or else you're looked at like an albatross around the neck of others for the rest of your life, and will find it very difficult at best to find a proper job.
On the other hand, like I said, if you do manage to get hired, you're expected to work for that company for life, and the expectation is that the company will take care of you as well (though they frequently do not, and do not take care of issues of power harassment from middle / upper management, either). Generally speaking, mental health issues also still have massive stigma in Japan, so the effort is frequently to hide the issue rather than do anything positive about it, and to continue on like nothing is wrong.
It really depends on the company, but if it's an old-school company with old-school board members, it's highly unlikely they'd let go of a worker for any reason at all unless they caused such a massively public ruckus that there was no choice (we're talking about criminal charges that are extremely public, not this rambling senility). So, in this guy's case? Yeah, he's probably got a job until either his relatives force him to retire by getting a medical order, or he dies / stabs someone.