One of the main antagonists of the series, Shinsuke was a former comrade of Sakata Gintoki's and Katsura Kotaru's during the Amanto invasion. He gained a fearsome reputation for assassinating many of the Bakufu's main officers. He was also planning a large-scale coup d'état, but vanished after the war ended. Now, he leads Kiheitai, a radical Joi faction and is in the Shinsengumi's list of worst criminals.
Very convincing cosplay! Although the photo is a little dark, we can still see his signature colorful kimono. I love that creepy look he's giving the audience. Thanks to Vento for emailing this!
EDIT: Thanks to Nocturne for letting me know that the cosplayer is Lithium Flower from Deviant Art!