You will work OVER 40 hours per week without getting paid overtime.
You do not get a lunch or a break. You are expected to eat your lunch with students (babysitting) and to eat the same food that they are given.
You will be required to sometimes work evenings without pay. They say this time will go into a "time off" bank, yet time WILL be missing and, again, you will not be paid since paid time off is at THEIR discretion. You will only be allowed to use paid time off when it suits them. This will usually be offered at the most inconvenient times and in one-off days here or there; hardly useful.
You are expected to answer calls or emails on your days off and drop what you are doing to accommodate them.
You will NOT be paid fully for transportation. This is especially bad if you must go to more than one school since you can't then buy a monthly pass to save money. This means that the already VERY low salary takes another hit.
BEFORE taxes and other deductions, my hourly pay worked out to about 1200yen. You can make more at IKEA or Costco and get benefits on top of that, which is wherre I'm off to.