Ukyo and Sakyo Jinnai are both identicle twin brothers and they are both skilled samurai which make their first appearence in Tenchu: Wrath of Heaven.
They are part of an organisation known as Muzen who act as contract killers at odds with Tesshu's underground group and they are also in league with the wizard Tenrai during the events of the game working against the azuma ninja in both Rikimaru and Ayame's story while making their last appearence in Tesshus story as the main antagonists.
Both Ukyo and Sakyo are skilled warriors with Sakyo using his brother Ukyo to lure their victims into a trap, Ukyo sets the trap while Sakyo does the killing and this ensures that their targets dont know their is two of them untill it is too late. During Rikimarus story when he is passing through the Ronnin village Ukyo keeps watch of his actions and sends various Ronin after him to hinder his progress. During Ayame's story Ukyo fights with Ayame at the abandoned temple while searching for one of the three jewels, during the battle Sakyo prepared to strike Ayame from behind but was stopped by Tatsumaru who later informed him at Tenrai's fortress that he was the one who would kill her.
During Tesshu's story Ukyo ambushes Tesshu at a waterfall at the Buddah temple while awaiting payment for killing Ganda and imprisons him in the limestone cavern but Tesshu uses one of his needles to open the cell after Ukyo orderedhim to kill his boss. After his escape Ukyo and Sakyo both visited the cemetary ahead of Tesshu and killed the informant who was going to pay Tesshu and later arrived at the Ronnin village in search of his boss who is later killed possibly by them. Before his death he gives Tesshu a final job which is to kill both Ukyo and Sakyo Jinnai leading to one last confrontation in the Ronnin village. Tesshu kills Ukyo and orders Sakyo Jinnai to reveal himself explainig that he knows how Ukyo is used as bait to set the trap for Sakyo to kill their victims, the pair face each other with Tesshu defeating Sakyo in battle. Before his death Sakyo reveals he has set explosives in the village which are set to blow anytime soon but Tesshu simply brakes his neck instantly killing him, Tesshu is then wounded by Ronnin in an ambush but kills his attackers and escapes the village as it explodes.