>“Not a Good Match”: Almost One in Three Japanese Graduates Quit First Job Within Three Years. While earlier generations saw lifetime employment as the norm, 30% of recent Japanese graduates quit within three years of starting their first job.

Looks like it used to be lifetime and now that is changing.

They probably are very clear to each other, it's us foreigners who read the signals wrong.

Because of that, there are proxy services that handle quit job for you. (though it's happened within this decade) https://www.taishokudaikou.com/

You don't quit jobs in Japan (traditionally, at least).