|First appearance||Eastman and Laird's Teenage Mutant Ninja Turtles #1
|Created by||Kevin Eastman
|Abilities||Skilled master of Ninjutsu
Excellent physical abilities
Experienced in hand-to-hand combat and numerous martial arts and karate
Enhanced Leadership skills
In all continuities, he was once a great and honourable ninja whose story is always closely intertwined with that of Splinter: he was the owner of a pet rat who becomes Splinter in the original comics, films and the 2003 cartoon series while Splinter was Hamato Yoshi in the 1987 cartoon series, the Adventures comics, and the 2012 cartoon series.
In the original comic book version (TMNT vol. 1 issue 1 (May 1984), Hamato Yoshi was a high-ranking member of the Foot Clan in Japan. He owned a rat named Splinter, who copied his movements as he practiced ninjutsu. He was romantically involved with a woman named Tang Shen. However, their relationship attracted the jealousy of Oroku Nagi, who also loved Shen. When Nagi was rejected by her, he became enraged and violently beat her. Shortly after, Yoshi arrived and, in his fit of anger, murdered Nagi. He was dishonored for having killed another member of the Clan and forced to choose between death or exile to the United States. He chose the latter, and left with Shen and Splinter. Years later, Nagi's brother Oroku Saki climbed the ranks of the Foot to become assigned the leader of its New York branch. He followed the two lovers to New York City and killed them both in vengeance of Nagi. However, the rat Splinter escaped to the sewers and mutated along with the Turtles. He then proceeded to teach ninjutsu to the Turtles as he himself had learned it from Yoshi, in order to have them avenge his owner's death.
In Tales of the TMNT #22, the turtles encounter a female ninja with a Shredder gauntlet on her arm; she vows to kill the turtles for crimes Hamato Yoshi committed against her family, but she is not a member of the Oroku family. This has the turtles wondering if Splinter was not telling them something.
In Turtles Forever, the original Mirage version of the Turtles mention that their "Master Yoshi" was killed by the Shredder which they one day will avenge.
In the 1987 TMNT cartoon and the TMNT Adventures comics that followed, Hamato Yoshi and Splinter are the same character, and the romantic subplot was eliminated.
Hamato Yoshi was once a member in good standing of the Foot Clan in Japan. Oroku Saki framed him for attempted murder of one of the Clan's leaders, and had him exiled to New York, where Yoshi was forced to live in the sewers in shame, and befriended the rats. Years later, when Saki moved to New York himself, he dumped mutagen into the sewers to kill Yoshi. Instead, the mutagen caused Yoshi and his four pet turtles to mutate. Yoshi himself mutated into a humanoid rat, as the last animal he was in contact with before he stepped into the mutagen were rats, even though he picked up the turtles just after he touched the mutagen and he tried to clean the mutagen off of them right before they mutated into their humanoid forms and took on the nickname Splinter as given to him by the turtles themselves because he could break wooden boards into splinters. He then proceeded to teach ninjutsu to the Turtles, to teach them self-defense because those who are different are feared by many.
In the episode "Splinter No More", Donatello finds a remedy to the mutagen effect and uses it to turn Splinter back into Hamato Yoshi. He thus returns to the surface and the streets, but finds it difficult to re-adapt into normal everyday human life. When the effects of the remedy wear off, Yoshi turns back into Splinter and returns to the Turtles with few regrets about leaving his human life behind.
In the Japanese dub of the 1987 series, his name is "Takeshi Yoshihama" (吉浜武士 Yoshihama Takeshi).
Yoshi's story, explained in the first of the four TMNT movies, mirrors that of the comics, although Oroku Nagi is completely removed from the story, and Yoshi's conflict is with Oroku Saki himself. Instead of fleeing from the murder of a clan member, Tang Shen persuades Yoshi to flee to America to avoid fighting Saki (presumably to the death) for her hand in marriage. Saki vowed vengeance and spent years searching for them. Saki eventually finds and kills Yoshi and his wife in their New York apartment, leaving Yoshi's pet rat Splinter homeless. The actor who played him was uncredited.
In the third Teenage Mutant Ninja Turtles film, the turtles save a child named Yoshi from a burning building in 17th century Japan, Michelangelo getting him out of the building and Leonardo subsequently performing CPR. This Yoshi's relationship with Hamato Yoshi is never fully explained, but based on the past incarnation of another character that the turtles meet on this adventure (a possible British ancestor of Casey Jones, Whit) a direct relationship between this boy and Hamato Yoshi seems implied. If this is indeed the case, then by saving the boy's life, the turtles had also saved their own future, as their origin is inexorably tied to the fate of Hamato Yoshi.
In the 2003 cartoon, Hamato Yoshi's background was once again thoroughly revised. He was no longer a former member of the Foot Clan. His new origins are described in the season 4 episode "A Tale of Master Yoshi".
Hamato Yoshi was an orphan, who, along with his best friend Yukio Mashimi, begged in the streets of 1960s Japan. When Yoshi returned a 5-yen coin dropped by the Ancient One, he took the two of them in for his honesty, and raised them both as his sons, training them in the art of Ninjutsu. The two boys grew up together in the same house, and learning the same arts. Unfortunately, they both also loved the same girl, Tang Shen, another orphan the Ancient One had taken in. Tang Shen loved Yoshi more. During this time, Tang Shen spared a rat that had sneaked into the house, and took it as a pet.
One night, Yoshi, Shen, and Mashimi observed a lone man being attacked by four ninja. The two young men decided to help him, and fought off the ninja. The man they saved was none other than the Utrom Mortu, and the ninja were members of the Foot Clan. Impressed by their skill, and having been partially exposed when his robotic arm was sliced off in the battle, Mortu gave Yoshi and Mashimi the offer to become Guardians, which they both accepted over the objections of their master.
As a Guardian, Yoshi was promoted time and again, but Mashimi never seemed to advance. Mashimi grew jealous as Yoshi surpassed him in every way, and in his anger, he murdered Tang Shen and betrayed the Utroms to Oroku Saki. Yoshi and the Utroms escaped. When Yoshi discovered what had happened he went into a rage, stormed the Foot's citadel and slew Mashimi in single combat.
With their Tokyo headquarters compromised, the Utroms relocated to New York, under the name of TCRI. Yoshi went with them, taking along Tang Shen's pet rat, which he named Splinter, to remind himself against the splinters of hatred and rage that drove him to kill Mashimi.
The Shredder eventually tracked Yoshi down, and tried to force him to reveal the location of the Utroms. Yoshi resisted, and was killed for his defiance. Splinter escaped and fled to the sewers, where he mutated along with the Turtles. He then proceeded to teach ninjutsu to the Turtles as he himself had learned it from Yoshi. In the "lost season" of the series, it is learned that Yoshi and the Ancient One had tried, in vain, to get the Ninja Tribunal's help in the fight against Shredder. They refused as he was not the 'true' Shredder even though the Utrom Shredder was growing in power. Due to their refusal to help, Splinter partly blamed the Ninja Tribunal for Yoshi's death.
Yoshi, a former Battle Nexus champion, is seen in flashbacks of the history of the Battle Nexus. A statue of him is in the hall of champions of the Nexus, and next to him are statues of Splinter and Michelangelo, who won the following two tournaments. Before the Utroms departed Earth, they gave Splinter an orb that contained a hologram of Yoshi. That orb was destroyed by the Shredder's adoptive daughter, Karai, when she attacked the Turtles' lair in the episode "Scion of the Shredder".
In the "lost" season five's final episode "Enter the Dragon Part II", a spirit of Hamato Yoshi appears, summoned by the combined power of the Turtles' dragon avatars, and defeats the Tengu Shredder. After delivering the final blow against the Tengu Shredder, he exchanges a brief greeting with Splinter before he disappears.
In the 2012 cartoon, Hamato Yoshi (like the 1987 series) was exposed to mutagen and is transformed into Splinter. In the introductory episode "Rise of The Turtles - Part 1-2", Splinter reveals to the turtles that in his life as Yoshi, he married Tang Shen and had an infant daughter named Miwa, and that they were killed in a fire set by Oroku Saki. It is rumored that Miwa (likely kidnapped by Saki and raised by him) grew up to be this show's version of Karai. Hamato Yoshi/Splinter is voiced by Hoon Lee.