One of three new Steel Samurai's after the original (played by Will Powers) was cancelled - The Nickel Samurai. Defendant of JFA case 4.
 

Personality: Matt is mostly a flake. He's naive, trusting, and leaves all decisions up to his managers (who he contacts frequently). He doesn't seem to care one way or the other about his predecessor or rivals.

 
Misc Facts: Matt has a cat named Shoe (Shuu in the Japanese, named for the creator). He also apparently likes wine and motorcycles.

In the Japanese, his Steel Samurai title is "Tonosaman - Hei."

Friends and Family: No known family, but his manager is Adrian Andrews, and he used to date Celeste Inpax.

Name Origin:
English: "Engarde", the French term people often say at the beginning of a duel, characterizes is rivalry with fellow performer Juan Corrida. (spoiler) It may also be that his dual persona necessitates him always being "on guard".

Japanese: Otoro is a kind of tuna, in the same vein as Niboshi (his Steel Samurai sempai). Outorou is also a rough Romanization of the English word "outlaw."

Background:

Actor who portrays the TV character the Jammin' Ninja, and victim of JFA case 4.
 

Personality: Unknown, though assumed to be possessive, competative, and bitter.

Misc Facts: He looks a lot older than he is. He also LOVES bears, and gets various bear toys and plushies from his fans by the dozens.

In the Japanese, the character he played was known as Ninja Nanja.

Friends and Family: No known family, though he was at one point engaged to his manager, Celeste Impax.

Name Origin:
English: "Corrida" comes from a term in Spanish referring to bullfighting. Ironically, in the Spanish version his last name was changed Rivera, after a famous bullfighter, as Corrida is actually a vulgarity (-Xan).

Japanese: Fujimi no Isao means "the invincible Isao." Which he is clearly not.

Background:

Adrian is Matt's manager, and a witness in JFA case 4.
 

Personality: When Adrian first appears in JFA she is cool, collected, and downright stoic. She has no interest in idle talk and is a model of professionalism. She's often seen with something in her hands.

When Adrian appears again in T&T she is much more at ease - cheerful, even excitable. She is self-conscious and aims to please.

Misc Facts: None.

Friends and Family: Adrian has no known family, but she once worked under Celeste Inpax, and is Matt's manager in JFA.

Name Origin: The only important part of Adrian's name is the fact that it sounds masculine, in all versions.

Background:

A man of many faces and talents. Witness in JFA case 4.

Personality: Precise, clever, and very professional. Killer values the bond of trust between himself and his clients more than anything.

Misc Facts: Phoenix compares his face to a baseball more than once.

Friends and Family: No known friends or family.

Name Origin:
English: John Doe is the police term for an unidentified dead body. "Shelly" is a reference to his calling card, the conch shell, and "de Killer" to his profession.

Japanese: Tanaka Tarou is the Japanese equivalent of John Smith (the most common, plain name you could think of).

Koroshiya literally means "assassin." Sazaemon comes from the word sazae, which means "a seashell." Sazaemon leaves a calling card with a seashell design whenever he commits a murder.

French: Pseudonym comes from "Allons au bistro", which means "Let's go to the pub". A Brinick is a type of shell.

Background:

A former manager, who committed suicide 2 years before JFA.

Personality: Unknown

Misc Facts: None

Friends and Family: Manager to both Matt and Juan, and also Adrian's mentor.

Name Origin:
English: Celeste was probably taken from her Japanese name (as in "celestial"). Her last name is rough Latin for "In Peace" (as in "rest in peace").

Japanese: Amano means "of heaven." Because she's dead.

French: Comes from the French phrase "La voute céleste", which is the sky or heaven. (thanks Akwatyka!)

Background: