In Sengoku era Japan, Tosa is a land where the Chousokabe family resides at Castle Okou. Kunichika heads the clan and plans to expand his territory through warfare for the prosperity of his people. However, Motochika, his son, disagrees with this approach and refuses to participate in the conflict. Enraged by his disobedience, Kunichika throws him into a river and disowns him. Miraculously, Motochika survives and washes up on land far from Castle Okou. Confused about why he is there and where Castle Okou is, he seeks answers from the locals. To his shock, they inform him that hundreds of years have passed since Sengoku era Japan, and the Chousokabe family has long been forgotten. Despite this revelation, Motochika struggles to comprehend the reality of the situation.
As fate would have it, he encounters Sakamoto Ryouma, a renowned revolutionary from the 1860s. Will Motochika assist him in overthrowing the feudal empire that he grew up in? What awaits these two characters who were never meant to cross paths? Their destinies are now intertwined, and they must navigate through time and space to uncover the truth about their past and future.