Hamato Yoshi

Hamato Yoshi (also known as Splinter) is the teacher and adoptive father of the Turtles. He was a Japanese man, who mutated into a rat. He is voiced by Hoon Lee.

Early life
When he was a young man, he trained in the same ninja clan with Oroku Saki. They used to be like brothers until they both fell in love with same woman. Her name was Tang Shen. Hamato loved her very much, and she chose Hamato to be her husband. Oroku Saki broke up their friendship and became jealous. One day, he insulted Splinter in front of him. He called him many things. Splinter felt he could not let those insults go unanswered. He then struck Oroku Saki for his insults. He lost his temper and over time, their rivalry festered into hatred. Later on, Hamato and Tang Shen got married and they had a beautiful daughter named Miwa. That evening, jealousy consumed Shredder. He broke into their house to fight with Hamato. As Tang Shen kept herself and Miwa to safety, Hamato did all he could to defend his family. During the fight, Shredder accidentally killed Tang Shen. Blaming Splinter, he set his house on fire from some nearby candles. Hamato was then left to his fate as Oroku Saki leaves with a severy injury from the burning house. Hamato survived, but he lost his beloved Tang Shen and supposedly his baby daughter.

Hamato then moved to New York City to get a new life. He adopted four baby turtles from a pet store. While he was walking, a strange man dumped into him. Something felt off about that man. He secretly followed him to an alley, but he accidentally stepped on a rat, which caused the strange man and his comrades to spot him. They attempted to harm him, but he fought them off. However, a canister of mutagen fell on him and he dropped his pets. He mutated into a mutant rat as his turtles become humanoid. Knowing he would not be accepted by people after his mutation, he quickly took his pets and fled to the sewers. He then raised the turtles as his sons. As the years roll by, he trained the turtles as ninjas. He then found a book of sculptors and painters of the Italian Renaissance. After reading his favorite artists, he gave names for his sons: Leonardo, Donatello, Raphael, and Michelangelo.

Turtles
Splinter cares and loves his sons since they were mutated. He raised them as his sons. He let Leo lead the team because he asked. He will also protect from the clutches of the Foot.

Tang Shen
Splinter love Tang Shen since he was still human. They both got married to have a beautiful daughter. However, during a fight with the Shredder, he lost his beloved Tang Shen. He still keeps a photo of her in the training room.

April
He becomes friends with April and then trains her to become a kunoichi (a female ninja). In Showdown, Part 1, April begins to ask Splinter why doesn't he go help his sons. Splinter says he's their teacher, it is his job to prepare them for all obstacles and challenges they face. Even when April still questions him, he angrily yells that he doesn't have to explain himself to a child. When April left with her father (who was brainwashed by the Kraang), Splinter told her it's too dangerous, bu April replied coldly that some of us can't just sit around and do nothing. When they returned, she apologized to Splinter for the words she said, but Splinter said there's no need because she spoke from heart, and he's relieved that she came back safely. Even after April reunited with the Turtles, Splinter still accepted April to be trained.

Leatherhead
He told him to stay away from his sons when he lost control.

Karai
It is revealed that Karai is actually Miwa. She was kidnapped by Shredder when she was a baby. He then raised her as his daughter. Splinter discovered she's his daughter during a fight in Showdown, Part 1. He refused to fight his own daughter, which caused Karai to call him a coward. He then left with a broken heart.

He has even told Leo that Karai is his daughter. Leo tried everything to have Karai learn that Splinter is her true father, but she refused to believe him. Later on, Shredder told Karai that Splinter is her father after she betrayed him. Since her rescue, Karai finally accepts that Splinter is her father, much to Splinter's joy. When she was captured and accidentally mutated, he was horrified by this. He became broken heart again upon seeing his daughter mutated. Karai became a mindless serpent and thinking Splinter as food (due to a snake being a rat's natural predator), but then she suddenly recognizes him before leaving.

Shredder
He and Oroku Saki were once friends, but they both fell in love with the same woman named Tang Shen. Even though Splinter "took" Tang Shen from him, she was never his (Shredder's). They both have a huge hatred after their fight in Japan. Splinter has become outraged that Shredder took everything that he loved (except his daughter). Even when Karai got mutated, they both suffered terrible pain in their hearts. They continue their vendetta on each other since then.

Trivia

 * This is the second incarnation of Splinter to be the mutant form of Hamato Yoshi. The first was in the 1987 series.
 * In the original stories and the 2003 series, Hamato Yoshi is the owner of Splinter, who was his pet rat.