Kikoku is a large version of the typical Japanese sword type known as nodachi. It has an oblong-shaped hilt trimmed with short white fur, a purple grip with two white rings around it and a yellow pommel, sheathed in a black scabbard decorated by white crosses from the opening to the bottom, and with a small piece of red rope tied near its opening. The said rope often varies in length in several forms of media, though it has so far been its longest in One Piece: Pirate Warriors 2, 3, and 4.
Due to its size, Law usually carries Kikoku over his shoulder (in contrast to other sword-wielding characters in the series, who either carry theirs on their hips or over their backs); yet in other times, he delegates one of his crewmates (namely Bepo) to carry it for him.
Law combines Kikoku with his Ope Ope no Mi powers, with the sword serving as a "scalpel" or an "injection needle" of sorts, using it to cut or pierce at a distance. At full power, Law can bisect an entire mountain or meteor. The sword could also block Doflamingo's strings, which is a notable feat as all weapons until then were easily cut by them (unless they were reinforced with Busoshoku Haki).
Amputate (切断,Anpyutēto?, literally meaning "Severance"): Law's basic offensive technique. Law cleanly cuts his target with Kikoku without actually harming them. Law's sword doesn't actually have to make contact with the enemy to cut the target apart. The separated body parts seem to maintain a connection similar to Buggy when using his Bara Bara no Mi powers. While Law has never called this technique before using it, he named it while explaining Radio Knife. Amputate also seems to be necessary when performing operations, in order to extract narcotics from patients, as he did so on the drug-addicted children on Punk Hazard. Law first demonstrated this move against a Marine soldier outside the Human Auctioning House in the Sabaody Archipelago, using it in combination with "Shambles". An "amputation" is the removal of a body extremity by trauma, prolonged constriction, or surgery.
Radio Knife (ラジオナイフ,Rajio Naifu?): An advanced version of Amputate. Law charges his sword with electricity in a similar manner to his Counter Shock move and then quickly slashes his enemy, which results in the target being separated into several segments while also suffering an electric shock. The cutting itself, like Law's regular slash attacks, is not harmful; however, it differs from them as it prevents the target from briefly being able to reattach their own body, and is meant to be a counter to any abilities where one can re-assemble themselves from Law's original amputation abilities. It was used for the first time against Trebol inside his ROOM after using Shambles to swap his position with Doflamingo. A radio knife is a surgical instrument that uses a high-frequency electric arc to cut away or through tissue. In certain spin-off games, Law tends to perform this move while doing an acrobatic flip, similar to how it was first used in canon, although this is not a requirement in other games.
Injection Shot (注射ショット,Injekushon Shotto?): While aiming at his target, Law rushes towards them with his sword stretched out in order to stab them. Once the sword connects, Law makes it "fire" like a gun, making the target bleed in the aimed spot while pushing them back a fair distance. Law's signature ability of being able to cut objects from afar can still be used while performing this move, as seen when he cut through Trebol's Hanamizu Shinken Shirahadori without having to touch it with his sword, but the move can still be blocked by hitting the blade from the side. It was first used against Trebol, but was interrupted by Doflamingo before it made contact. Its first successful use was against Doflamingo himself. A targeting reticule similar to his Scan also appears on Law's hands or on the blade itself while he is preparing the attack. Only the "injection" part of the attack's name is rendered in kanji, via its literal reading being "chuusha". Via its debut appearance outside of the manga in One Piece: Pirate Warriors 3, the gun-shot sound is not applied; while in Burning Blood, the force of the attack is enough to fire a blast of energy forward from a distance upon stabbing.
Sterben (死の刀,Suteruben?, literally meaning "Blade of Death"): A technique used when Law had his right arm severed by Doflamingo. After using Takt on his severed arm, Law makes it spin. Because the arm is still holding Law's sword, it effectively ends up acting like a buzzsaw that cuts the opponent in a vertical motion. It was first used to defeat Trebol. However, in certain spin-off games, the attack is instead used by levitating and buzzsaw-twirling the blade in front without Law's arm being detached and gripping it, along with purple energy that trails his sword emitted by his Radio Knife. Sterben means "to die" or "dying" in German, often used as a term for hospital deaths.
Anesthesia (麻酔,Anasusīja?): Law coats his sword with the essence of KROOM, allowing it to pierce through anything without harming the target, akin to spatial phasing. Law first used this against Big Mom.
Shock Wille (衝撃波動,Shokku Vire?, literally meaning "Shock Wave"): After piercing through a target with Kikoku, Law releases an electrical shock wave through it that fries the target from the inside. This move is very similar to Gamma Knife, but because the electric shock directly occurs from the inside instead of coming from the outside, it ignores whatever external defenses the target may have. It was first used against Big Mom, bypassing her normally monstrous external body defenses and making her bleed from the mouth.
Video Game Techniques
Resection (切除,Risekushon?, literally meaning "Cut Off/Ablation"): A technique only used in the video game One Piece: Gigant Battle! 2 New World. Standing in one side of ROOM, Law slashes from top to bottom. In surgery, a resection is the act of removing part or all of a body part, such as an internal organ; while an ablation is removal of material form surfaces of an object through erosive processes (such as vaporization and/or chipping). Used as one of his basic attacks, where it must be done via charging up his neutral basic attack input for around a second. The kanji's literal reading is setsujo.
Accident (不慮の事故,Akushidento?, literally meaning "Unforeseen Accident"): A technique only used in the video game One Piece: Gigant Battle! 2 New World. After getting into a crouching position on his knees upon landing from the air, Law creates ROOM with him in its center and slashes horizontally-outward via a sweeping slash. The kanji's literal reading is Furyo no Jiko, and is it used as one of his midair attacks.
Transection (切断,Toransekushon?, literally meaning "Severance/Amputate"): A technique only used in the video game One Piece: Gigant Battle! 2 New World. Standing in one side of ROOM, Law slashes from bottom to top. A transection is a division by cutting across or a cross-section along a long axis. Like his Amputate, it oddly enough has the same kanji and literal reading as the said technique (setsudan). This was due to the attack being named before Law named his basic Amputation ability in the manga/anime.
Catastrophe (カタストロフィ,Katasutorofi?): A technique that appears in the video game One Piece: Gigant Battle! 2 New World, where it is used as his strongest special attack. In the space created from ROOM centered around himself, Law cuts those within many times with rapid slashes as he slowly moves forward, then finalizes it by replacing the victim's head with a cannonball via Shambles.
A similar technique is also used as his inverted S3 (Triangle x2, Square) in the One Piece: Pirate Warriors games, where he simply cuts with his sword rapidly (flailing it around with a single hand) while standing stationary, and instead ends it with a Takt. The original version of the move can be somewhat replicated if Law uses his R1 ability to lay down another ROOM during the inverted S3 to instantly transition into the C5 (Square X4, Triangle) version of his Shambles.
In One Piece: Super Grand Battle! X however, this acts as Law's Secret Attack, and is a variation on his wide-scale slash used to defeat Vergo. First for the intro scene, Law forms a large ROOM to lift up a marine ship (via Takt) much like at Punk Hazard, then cuts it in half. A large ROOM on the arena forms as Law stands from the foreground, slashing away at the space to cut up all targets within it 16 times; then just like in Gigant Battle! 2 New World, he ends it with a Shambles via snapping his fingers to replace his target(s)' head(s) with an incendiary object, only he instead uses a blue bomb with a fuse (also used by the midair strong attack version of his Shambles in the same game). However, in Pirate Warriors 4, it becomes his airborne C5 (Square x4, Triangle) instead.
Kaitengiri (回転斬り,Kaitengiri?, literally meaning "Rotating Cutter"): Law draws Kikoku for a spinning slash attack forward. Used as his side weak attack in One Piece: Super Grand Battle! X, where it can be tapped for more spins/hits while also having enhanced range via ROOM. Can also be used in midair akin to Senkaigiri, only at a forward angle slanted-upward (though he first delays himself in a small drop then rises upward-forward after the first two spins).
Kiriage (斬り上げ,Kiriage?, literally meaning "Slashing Lift"): Law slashes upward in an outward slash to launch his target. Used as his upward weak attack in One Piece: Super Grand Battle! X, where it can have enhanced range via ROOM.
Nagiharai (なぎ払い,Nagiharai?, literally meaning "Mow Down"): Law's neutral strong attack in One Piece: Super Grand Battle! X, where he slashes outward across in front of himself. Can have its range enhanced by ROOM. It should be noted that the term "nagiharai" (lit. mow sweep) is a term for "mowing down", with the "nagi" part being written in hiragana instead of kanji (薙ぎ).
Kiri Oroshi (斬り下ろし,Kiri Oroshi?, literally meaning "Slash Dropping"): The followup to Nagiharai via second input, where Law reaps downward with Kikoku. Used in One Piece: Super Grand Battle! X and can have its range enhanced by ROOM.
Senkaigiri (旋回斬り,Senkaigiri?, literally meaning "Swiveling Cutter"): Akin to the aforementioned Kaitengiri, only Law rises upward at a slight forward angle; can also tap the button for more spins/hits like the said Kaitengiri as well. Used as his upward strong attack in One Piece: Super Grand Battle! X, and can have its range enhanced by ROOM.
"Mo dare mo hikikaesene-!" ("もう誰も引き返せねェ!","Mō dare mo hikikaesene-!"?, literally meaning "No one is ever going back!"): Used in Pirate Warriors 2 and 3 as his Level 2 Special Attack. Law creates a large ROOM, then tosses his up his sheath into the air and pulls Kikoku back with both hands gripping it over his shoulder. He then does an extremely wide slash that affects the entirety of the said ROOM, then afterwards catches his sheath to re-holster Kikoku. This is most likely a nod to his finishing slash against Vergo which split the majority of Punk Hazard in half; the quote for the name of this attack is also the same one Law speaks word-for-word, only he does not speak out its name in-game until Pirate Warriors 3. In the game's English release, the technique is called "No one will go back!".