Tosa, the feudal province which is now known as Kōchi went through much of the turmoil of changing factions and civil wars. By the Sengoku Jidai the Chosokabe clan managed to unify their entire province. Shikoku, the island nestled between Kansai and Kyushu, literally means four countries. Chosokabe Motochika managed to unify these four provinces under his rule. However, another unifier, Toyotomi Hideyoshi was in the middle of trying to unify all of Japan and defeated Chosokabe pushing them back to Tosa.
Despite being quite prominent, Chosokabe Motochika is seldom mentioned. A possible reason for this is that a few years after Hideyoshi’s death, Tokugawa Ieyasu went to take control of Japan. Chosokabe supported the Toyotomi side, the losing side and as a result was wiped from existence and replaced with the Yamanōchi family. Those who were fromthe Chosokabe were all stripped to lower ranks and for the next 260 years suffered and had their childrens suffer possibly the worst prejudice in Japan at that time. Well for mainlanders at least, but the Ryukyu and Ainu are a totally different story.
Chosokabe’s regained a bit of fame in popular (nerd) culture lately, they were featured in Shogun Total War 2, Sengoku Musuo (“Samurai Warriors”) and Basara, which I’ve never seen. In the later two depicted very flamboyantly, which doesn’t seem to be based on anything except that maybe Kōchi people like to drink… a lot.