Sounds like your employer is pretty shitty (and to be fair, Japan has more than its fair share of shitty employers), but that's an attribute of your company, no

Sounds like your employer is pretty shitty (and to be fair, Japan has more than its fair share of shitty employers), but that's an attribute of your company, not Japan itself. And if you're coming over on a startup visa, it's your company and you set the rules. All that said, it's hard to people with no connection to Japan opting to start up in Japan -- as patio11 notes, doing so without fluent Japanese is playing life in hard mode.