[Sangetsu]

A contract written in "barely competent" English is likely written by a less-than-competent employer, and probably not by a real attorney.

Your contract should be renewed every year, any terms you agreed to in a one year contract will not apply after one year has passed.

You are not required to give any notice whatsoever if you are going to quit. You can walk out tomorrow, and there isn't anything they can do about it, and they certainly cannot hold back any pay if you fail to give them notice that you are going to quit. I would give them one or two month's notice, just so they can find a replacement, but that's all.

You should be paying two types of taxes, income tax, and residency tax. Normally the income tax is withheld from your salary each month, and you would be responsible for your residency tax beginning in your second year in Japan.

You should have received a certificate showing your tax payments, and a tax adjustment form once per year. Your city office should be sending you a bill for your residency tax once per year.

If you have properly registered with your local ward office, you should be receiving these papers, unless your employer has not submitted the proper paperwork with them.

These taxes must be paid, if they are not paid, then they accrue penalties. If your employer has not been paying your income taxes, you need to go to the labor office and file a complaint as soon as possible. Take a copy of your contract, and whatever pay slips you have, they should show any tax payments or deductions.

You can quit any time you like, and there is nothing which your company can do about it. You should be hunting for another job right now, so you are employed when it comes up time to renew your visa.