Home ⼎ Sekigahara & Tosa
00 — Origins
In 1600, Chosokabe Morichika, who had backed the losing western army at Sekigahara, forfeited the whole of Tosa. Yamauchi Katsutoyo arrived in his place — and that single changeover would define Tosa's caste structure, and its politics, all the way to the fall of the shogunate.
The Chosokabe were, in their day, the dominant power across nearly all of Shikoku. Their military strength rested on the "ichiryo-gusoku" system — farmer-soldiers who tilled their fields in peacetime and grabbed a set of arms to rush into service the moment they were needed. It was a cost-effective way for a small domain to field real numbers. After the clan's defeat, most of these men were absorbed by the incoming Yamauchi as a new, lower samurai class: the "goshi."
Stories still circulate in Kochi today — that a goshi had to step off the road and bow to the ground when passing a joshi, that even the color of one's rain gear was regulated. Recent scholarship confirms real institutional gaps (where you could live, which posts you could hold, restrictions on changing occupation) while finding no law that regulated everyday conduct in that much detail; some of these vivid details appear to have been embellished by later storytellers and novelists. What historians broadly agree on is this: however accomplished a goshi might be in learning or wealth, an institutional ceiling kept him from ever becoming joshi — and that ceiling built up real, lasting resentment.
What matters is how this rivalry detonates, unexpectedly, at the end of the Edo period. Sakamoto Ryoma, born goshi, and Iwasaki Yataro, born into the even lower "jige-ronin" class, both ended up on the side that broke the existing order — arguably because, standing outside it, they had the least to lose. The same structure later produces the leaders of the Freedom and People's Rights Movement. More on the Late-Edo Patriots and that movement on their own pages.