Nothingness: The ultimate mental state a swordsman can obtain, being achieved only by swordsmen of the highest order. It corresponds to the concept of Suigetsu of the Yagyuu Shinkage-ryū. One is nothing, and is thus
invincible. As they have nothing above them, they become an unreachable sky that can't be touched. Not even a slash that uses the Multi-Dimensional Refraction Phenomenon can reach someone with no sky. Only a
swordsman who has reached the mental state of infinity can perceive this.
Munenori is a "Sword Saint" that is praised as "Peerless in Swordsmanship" by his peers. He has perfected his swordsmanship and mental state to the point that
Musashi Miyamoto states that she's outmatched by him even after she reached nothingness and grasped Zero. Due to his mental state, Suigetsu and his perfect technique, Munenori is able to react to any opponent and wield his sword without exerting any force on his body, allowing him to swiftly cut down his opponent before they can tell when he draws it, to the extent that he is able to cut down seven warriors in an instant. In addition to his mastery of the sword
Using this technique, he is capable of accounting for all possible outcomes of a situation, and staying a step ahead of all of them. It is so absolute that Musashi had to create a completely new possibility to manage to bypass this technique.
Assassin is a peerless swordsman, having reached a realm transcending the realm of men through nothing but hard work and single-minded dedication. He is stated to have the greatest swordsmanship amongst all of the Servants in the war, far surpassing
Berserker, who is more than qualified for the Saber class, and
Saber, who is renowned in life for being one of Britain's finest knights. Even
The King of Heroes is no match for him in a contest of swordsmanship. Furthermore, he can clash evenly with his chief rival,
Musashi Miyamoto, who had also reached the pinnacle of swordsmanship and could collapse all possibilities into a single outcome, with their respective skills being stated to transcend time and space itself. As such, his skill as a swordsman is stated to have reached the state of true emptiness, reaching the unreachable existence of Infinity.