Doing taxes as a sole proprietor

I own a small English school, about 45 students, 1 guy who works on Saturdays and pays me each month. No employees. In the past the previous owner used an accountant, his wife did an excel for all incoming/outgoing expenses and passed it on to him. Long story short, how difficult is it to do the blue form? Due date My Japanese isn't great but my wife is Japanese. Is the due date March 15th? Have to decide whether to try myself or go with the accountant. Thanks for any help.

by Shidapack