Interesting report in the Japan Times, March 29, 2015 India interested in buying Japan's Soryu-class submarines :
This is just prior to Indian Defence Minister Manohar Parrikar visiting Japan including meeting with Defence Minister Nakatani.
Regarding "Parrikar noted that Japan had strict regulations on the export of defense technologies but that the rules are changing." in the article above. Japan should be well aware that India is close to Russia on high tech submarine issues. India has even financed Russian ship and submarine repairs/renovations. India is leasing a Russian Akula II class SSN (now INS Chakra - was Russian Nerpa). So future dangers might exist of Soryu materials, designs and specifications finding their way to Russia.
Japan might also wish to note India, like most great powers, plays hard-ball as a defence customer which sellers like France find difficult. India may already be playing hardball "Parrikar suggested that India is not likely to make a decision anytime soon on whether to purchase [ShinMaywa] US-2
See more details of France's experience at Indian Possible Interest in Buying-Building Japan's Soryu Submarine - Australia, January 30, 2015