Japan commercial visa for 1 year

please help me to make a letter for a commercial visa for japan for 1 year.ive been to japan several times alrdy but the can give me only 2 or 1 month visa.i want it a 1 year visa cause its hard for me to apply everytime i go,for a business purposes.sometimes i want to tay more than three months.if they can give me that visa. thank you very much!..........asap.