What will happen if I leave Japan with an expired work visa and no travel visa?

My visa expires on the 12th, and I will leave on the 15th or 16th. I could get a travel visa for 4000 yen, but I don't want to spend the cash if it's not a big deal. My biggest concern is that they will keep a record of my malfeasance and then not letting my back into the country in the future.

Get the tourist visa! You will be discovered when you go through exit controls and it is possible that you could spend a night in detention-which you will have to pay for!. I know it makes no sense that they would prevent you from leaving, but they will have to interview you which could make you miss your flight. Once they have you in their custody they have to keep you until they can get you on a plane which obviously could be the next day. The amount of time you overstayed is moot when it comes to being flagged-the officer who flags you is unlikely to have any discretion over this. You just have to wait until his supervisor has time to interview you and decide what will be done with you. You will be deported as an overstayer and thus have at least a one year exclusion. It's just not worth it for 4000 yen.

simple - you cannot go back to Japan. do not want to spend money on travel visa - then stay back in your home country.