Amakusa Shōgo (birth name: Mutoh Shōgo) is loosely based on an actual historical figure. When Matsukura became daimyo of Shimabara (a region on the west coast of the island of Kyushu) in 1633, he raised taxes drastically and tortured those who could not or would not pay. This led to the Shimabara Tax Rebellion of 1637-1638. At first, it attacked the daimyo, then spread to nearby areas, including the island of Amakusa. There, they found a figurehead for the rebellion: a devout teenage Christian named Amakusa Shirō Tokisada, who was the basis for Shōgo. Eventually the shogun's troops trapped the rebels in a castle and laid siege to it for three months. Both sides suffered casualties before the siege ended, and Shirō Amakusa was among the dead.
Shōgo was a prodigy swordsman, able to master the Hiten Mitsurugi-ryū by the age of 14, and to such a degree that he was able to wield its most basic techniques beyond God Speed/Ien shinsoku, being able to surpass Godspeed without the need of a two step Batto-jutsu/Sword drawing-technique, like the ōgi/Secret technique (Amakakeru Ryū no Hirameki) of the Hiten Mitsurugi-ryū, which is an accomplishment rarely seen in true successors of the Hiten Mitsurugi-ryū.
Not only limited to the physical and precise, Shōgo's genius was able to have created the first new technique in 13 generations, creating a new Hiten Mitsurugi Ryū technique, the Rairyūsen (Thunder Dragon Flash). Unique to him, the technique involves utilizing his swordsman's spirit and ki, through which the correlation of Aoshi, believed the technique to be of the same variant of the kinds of attack similar the Shin no Ippo used by Udo Jin-e. Combining it with light reflected from his sword, the series of flashes that emanate from the blade impose such will and strikes the opponent by their sense of sight and mind so powerfully to where it is able to knock them out by sheer force of awe and spirit. By his discretion, Shōgo is also able to level its intensity; its normal strength was capable of knocking out legions of forces hired to stop him, and in direct example, was capable of paralyzing Misao Makimachi's mind through her sight, knocking her unconscious; its most powerful is enough to paralyze the eyes and permanently blind its foes.
Despite his impressive skills of swordplay and kenjutsu, Shōgo had not truly attained by right of traditional succession the mantle of the next generational master of Hiten Mitsurugi-ryū; while he was able to deduce and mimic the Amakakeru Ryū no Hirameki, his succession was rather attained by the use of his Rairyūsen than the Amakakeru Ryū no Hirameki and the trial of the Kuzuryūsen proper, which is crucial to understand the basis of heart and principle the art follows. In turn, while he is a master of its external capabilities, he is not yet a master of its internal aspects that guides its users, and is what truly defines a true master and user of Hiten Mitsurugi-ryū.
Shōgo was said to be the "Son of God" and he lead a rebellion with the Shimabara Christians to fight against the Meiji government. When he was young, he was forced to leave Japan with his younger sister, Sayo (or Lady Magdalia), and his uncle, Nishida Hyōuei, in order to survive the persecution of Christians by the Tokugawa regime. His parents were both brutally killed by Christian persecutioners, soon before his uncle Hyōuei was able to take he and his sister Sayo away.
Besides Kenshin and his master, Hiko Seijūrō XIII, Shōgo is also a disciple of the Hiten Mitsurugi-ryū after being trained by his uncle Hyōuei who failed to become Hiko Seijūrō XIII, since he couldn't master the Amakakeru Ryū no Hirameki and so beat the Kuzuryūsen of his master in the final challenge. Nonetheless, Hyōuei survived his master's Kuzuryūsen and left Japan to carry on with his life. He later returned to save Shōgo and Sayo from persecution.
From their duel, Kenshin learned that Shōgo wasn't a bad person. Quite the contrary, he was a very compassionate and kind person deep down in his heart, and he never wanted to kill another person. In fact, he suffered unspeakable torments every time he took a life of another. Kenshin decided to fight Shōgo one last time in order to bring him back to the light, to stop calling himself a deity, and admit to himself that he is nothing more than confused and doesn't like hurting human beings, like any other. The two confronted once again, both with their Amakakeru Ryū no Hirameki techniques, and Kenshin won. Shōgo admitted then that he never wished to take another life, that he regrets everything that he had done, he even asks Kenshin to end his life, although his followers convinced him to keep on living and guiding them.
After some time in jail, since he gave himself in to the authorities in order to pay for his sins, the Meiji government decided to forgive Shōgo but also to exile him and his people forever. Holland accepted to receive every single one of them. So, after a very sad farewell, first before his sister's grave (reading her last letter to him) and then with Kenshin, and the rest of the group at the dock, they left by boat.
Shōgo has long brown-red hair and yellow eyes. He is always shown wearing a long green cape and a gold circlet (Shirō, in comparison, was reputed to be a bishonen—beautiful boy—but this may have been legendary, as well as a comparison to another mythic bishonen commander, Yoshitsune of the Minamoto clan, who fought in the Heike Wars of the 12th century.)
Shōgo Amakusa is a kind-hearted person to his fellow Christians and especially to his younger sister, Sayo. He would do everything in his power take care of his people and improve their lives, and in the face of persecution and injustice, even rise just to fight for them and their beliefs. He is also very faithful and devout to the Christian God.
However, his hate for the Meiji Government shrouded his heart in darkness, making him somewhat of a ruthless person. With this, he was able to kill three powerful people from the government, which lead the citizens in Japan worried.
During their battle, Kenshin saw that deep in Shōgo's heart, he never wanted to kill anyone because of his sadness and pain. Evidently, Shōgo did not like this in the least as he sealed Kenshin's eyesight as punishment.
Amakusa Sayo - sister
Nishida Hyōei - uncle and former master