(高杉晋助 Takasugi Shinsuke), Seiyū - Takehito Koyasu

A former comrade of Gintoki and Katsura, and a major antagonist. He now leads a radical Joui faction called the Kiheitai and is known amongst the Shinsengumi as 'the most dangerous man in both the Joui faction and amongst the radicals'. He is easily recognisable through his bandaged left eye, his colorful kimono, his eerie smile, and the pipe he is often seen smoking.

He, Gintoki, and Katsura studied in the same temple elementary school when they were children, and he fought with them against the Amanto invasion during the latter part of the Joui war. After the war ended, he vanished, and has since gained a dangerous reputation due to his assassination of many of the Bakufu's main officers and his planning of a large-scale coup d'etat. Before his first appearance in both the anime and the manga, he was mentioned to have fled Edo and to have been hiding in Kyoto, although it is unclear how long before this was.

Unlike Katsura, he does not seem to be interested in saving the country: rather, he now believes that the only way to save it is to destroy the "rotten" post-Joui war world. He is particularly resentful about this, as he claims that it has stolen their teacher- Shouyou Yoshida, who instructed him, Katsura, and Gintoki on the ways of the samurai- away from them. Although he listened to Katsura's attempts to change his mind, his antagonism with them drove him to make dealings with the space pirates "Harusame" in order to drive them off, offering Gintoki and Katsura's heads as the ticket to join. The Harusame gladly accepted, as they were resentful of Gintoki and Katsura for an earlier defeat. Takasugi later attempted to start chaos in the Shinsengumi by planting a traitor, Kamotarou Itou, in their ranks.

Takasugi mainly appears in the long parts of the story, and is described as a character who 'possesses a serious atmosphere'. Although there has been little shown of his personality, he genuinely appears to hate the society that they currently live in and seems intent on changing it, even if it means completely destroying Edo on the process. The author (Hideaki Sorachi) himself mentioned in the character formula book that he 'hates change', which provides another reason for his hatred of the changes that the Amanto brought about. He is shown to like festivals, although this is mainly due to the opportunity they provide for a large-scale terrorist attack: he appears to have an attraction to ruin that is almost nihilistic. He also appears to have considerable insight due to his 'seeing through Itou's heart' and subsequently planting him in the Shinsengumi's ranks.

Source: Wikipedia