Legato Bluesummers (レガート・ブルーサマーズ, Regāto Burūsamāzu) is a man who devoted himself to Millions Knives, and makes it his main goal to have Vash the Stampede experience eternal pain and suffering. He's the secondary antagonist of the Trigun series and serves directly under Knives, which also gives him command over the Gung-Ho-Guns, especially while Knives is injured as a result of the July Incident. He is the only one of the Gung-Ho-Guns without a number, as pointed out by Elendira the Crimsonnail, which means he's far less dispensable to Knives than the rest of them.
Prior to the beginning of the manga, Legato was a nameless sex-slave. While imprisoned, he slowly developed his power by weaving metal threads into his brain, allowing him to take control of other bodies. Before he could fully develop his power, he was discovered, wounded, and raped. However, Knives happened to pass by and destroy the city, with Legato being the only survivor thanks to the power of his threads. Legato immediately becomes infatuated with Knives and swears eternal loyalty, showing his willingness to allow Knives to kill him. Knives takes the boy in as a tool, and presumably gives him the last name Bluesummers.
Later, Legato and Dr. Conrad found July in ruins and Knives heavily wounded. Legato sees Vash in the distance, and realizes Vash is the cause of Knives's serious injury, but Conrad convinces Legato to help tend to the wounded Knives instead of chasing after Vash. Seeing Knives in such a state traumatizes Legato, who swears revenge on Vash, eventually leading Legato to plan a killing game to torment and eventually kill Vash.
Legato first appears in the manga claiming to be a messenger, introducing Vash to his proposed killing game. He warns that Vash will be pursued by "demons" who are intent on killing him. Legato leaves Vash a Coin Case, telling Vash that each of these assassins will be carrying a coin. He tells Vash that once he has collected all of the coins something will happen. When Vash asks his name and how he knows these things, Legato formally introduces himself and then hints that Knives sent him. Legato later watches the battle between Vash and the first two members of the Gung-Ho-Guns, Monev the Gale and E. G. Mine. Upon defeating Mine, Vash challenges Legato, stating that he intends to reverse their roles of hunter and hunted in Legato's twisted coin game.
Legato first demonstrates his ability to control the bodies of others in a restaurant. When assaulted by a group of slave traders, Legato uses his powers to kill the man by forcing him to tear out his own heart. He then kills the other men that had been with him by making them shoot each other. Legato tells the women that they are free now and warns them to be careful as "humanity will soon come to an end". Leaving the restaurant, Legato realizes that his previous action was an unusual display of emotion on his part, and that Vash's challenge has greatly bothered him.
Following the battle between Vash and the third member of the Gung-Ho-Guns, Dominique the Cyclops, Legato gathers with the Gung-Ho-Guns for Knives's reawakening at Jenora Rock, which Vash senses and rushes to. Upon being reawakened, Knives twists Legato's neck in an 180 degree angle and then breaks his limbs when Legato instinctively moves to attack Vash. Elendira later comments that this was also influenced by the fact that Legato had used the Gung-Ho-Guns to settle his personal vendetta against Vash, and that it is amazing that Knives should decide Legato's life was worth sparing at all. Legato's wounded body is then placed in a coffin that is chained shut except for the head area. He uses his controlling powers on a large ogre creature to serve as his transportation. The creature is killed and Legato forcibly taken back by Elendira following the battle between Vash and Hoppered, and Legato is placed in a new coffin with primitive metal limbs.
When Vash and Wolfwood finally reach Knives, Legato uses his abilities to restrain Vash as a prisoner for eight months straight, which greatly weakens him. Wolfwood later betrays the Gung-Ho-Guns and rescues Vash, shooting the weakened Legato in the back of the head. The wounded Legato is left in a catatonic state, with his body slowly breaking down. However, Legato reveals a full recovery in time to save Knives from Zazie the Beast, where it is revealed his power functions through the use of microscopic strings that connects his mind to the muscles of his victims. While in confinement in his coffin, Legato developed his power further to restore his broken body to fuctional form.
In the final stage of Knives's plan, Legato faces off against Vash in order to prevent Vash from getting to Knives, revealing that the now completed Coin Case functions as a device that blocks Legato's abilities to make their battle more interesting. As Legato and Vash do battle, Legato reveals his past as a sex slave, and how he came to love and swear loyalty to Knives for destroying the city he was trapped in. Legato beats Vashs so severly that it activates an automatic defense power in Vash, which severely wounds Legato. Vash destroys the coin case in an attempt to even the battle once again, and the two clash one final time, both of them pushed to the absolute limits of their strength.
Once defeated by Vash, Legato demands that Vash finish him, threatening the life of Livio and everyone else Vash holds dear. Feeling he has no choice, Vash shoots Legato in the head and Legato dies smiling.
The anime shows Legato in a less sympathetic light. In the anime, Legato is far less emotional than his manga counterpart and it is never explained why he joined Knives. Legato is simply a sadistic nihilist who is determined to torment Vash and aid Knives in his quest to eradicate humanity. He also attached Vash's severed left arm to himself in place of his own, because Vash "refused to be by his (Knives) side". He also displays a habit of licking the transplanted hand while taunting Vash.
Legato has a similar introduction to the one he is given in the manga, the key difference being that in the anime Legato does not play the game with coins with Vash. Legato uses The Gung-Ho-Guns to place Vash in situations where he must either kill or be killed. Vash never ends up killing though, always figuring out a way to survive without finishing anyone off. Vash still gets scarred by Legato's actions, as most of the Gung-Ho-Guns either get killed for failing to put an end to Vash or commit suicide because they were afraid of being punished by Knives.
When Vash finally has Legato cornered, Legato reveals that he is going to allow Vash to kill him. Vash refuses. Legato insists that it is okay and that he has no reason to continue living. Seeing that his words are not working on Vash, he threatens to kill Milly and Meryl if Vash doesn't finish him off. Feeling like he has no other option, Vash shoots Legato in the head. Legato dies smiling, knowing that his death will scar Vash for life.
In the anime, Legato has the ability to use psychic powers to manipulate people. He obtained these powers from Knives who gave Legato Vash's left arm, which was endowed with some of the god-like powers the brothers possess. When he does this, it is usually to make a person or a group of people do something against their will. Examples of this include when he made a group of men from the Roderick Gang kill one another, making an entire population of a town disappear, controlling Chapel the Evergreen to kill Nicholas D. Wolfwood, and cramming a group of soldiers into a tight truck by manipulating their bodies.
In the manga, Legato uses metal threads, implanted in his brain, to control others as well as create barriers. The biggest example of when he used this was with his first encounter with Knives as a child. He used this power to survive Knives' attack and impressed the killer to allow him to be his right hand man.
- "Legato" is a musical term that means to play "smooth and connected." while in Latin "Legatus" means ambassador/commander
- "Bluesummers" is a likely reference to blues music.
- In the manga, the skull on Legato's left arm opens up to reveal a mechanical spindle with all the micro-wires he uses to control people. It is merely decorative in the anime.
- Legato is openly gluttonous in both the anime and manga.