Answers for question 1 and 2

1.Since when were guns illegal for citizens to hold in Japan?
2.Who made the law?

The gun control in Japan became strict after the Second World War in the late sixteenth century.
Since then, the gun control had been expanded around Japan durring the Towkugawa period (1603-1867). The law began in 1588, when the ruler of Japan, Toyotomi Hideyoshi announced the Sword Hunt, also known as the "Katanagari", and was recently revised by the current government. In 1958, the law was renamed and is no known as the Firearm and Sword Possession Control Law(Jyuhou Touken-rui Shoji-tou Torishimari-hou)

Bibliography
https://www.loc.gov/law/help/firearms-control/japan.php
http://www.theatlantic.com/international/archive/2012/07/a-land-without-guns-how-japan-has-virtually-eliminated-shooting-deaths/260189/