Sakamoto Ryoma is a popular low ranking rebel samurai who helped prepare Japan for the Meiji Restoration. He was crucial in the creation of a modern navy. One of his most notable accomplishments was persuading the rival Satsuma and Choshu clans to work together to overthrow the Shogunate. That an uncouth roshi, a 'disgrace' to bushido - who had been denounced by his own clan - could acheive this seemingly impossible task made him a national hero.
He also topped a survey of historical figures one would most like to have a drink with (according to a survey of 1,558 people conducted by Asahi Breweries Ltd. last summer). All 47 prefectures including Tokyo have at least one private fan club dedicated to Ryoma with over 13,000 registered fans.