Famed manga creator Ken Akamatsu (Love Hina, Negima) has warned that if doujinshi (self-published manga) based on others’ works are banned as the result of a new trade pact involving Japan and the United States, that “the power of the entire manga industry would also diminish,” according to Hachima Kiko via Anime News Network
Doujinshi based on major manga properties are tolerated by the Japanese publishing industry, and are seen by many (like Akamatsu) as contributing to the community of fans that support the largest comic publishing industry in the world. The annual Comiket convention, which is a marketplace for the display and distribution of doujinshi, attracts over 500,000 people over three days. Although this is a turnstile attendance (counting a three-day attendee as three attendees, vs. San Diego Comic-Con or New York Comic Con, which report unique attendees), that still probably makes Comiket the largest comic convention in the world, so it’s hard to argue that doujinshi aren’t a critical component of Japanese comic culture. 
The proposed agreement between the United States, Japan, and seven other Pacific countries would standardize copyright laws in all the countries. The provisions affecting doujinshi mean that copyright violations can be brought without a complaint from the injured party. That would be a big change for Japan, where copyright holders don’t prosecute doujinshi creators who self-publish in small quantities. The new laws would also provide for damages to be paid by violators   
Perhaps given the relative success of the manga industry in Japan, American copyright laws should be changed to mirror Japan’s rather than vice versa.