Splinter's History
Childhood and rise to fame
Hamato Yoshi is a descendant of the Hamato ninja clan who defeated the Shredder 500 years ago and trained themselves to be warriors to fight against the Foot Clan and prevent the Shredder's return. When Yoshi was just a boy, he heard the story of how the Shredder was defeated from his grandfather, Sho, but on that same day, Yoshi's mother, Atsuko, left her father and son so that she can perform her duty as a Hamato, which greatly saddened Yoshi.
For many years afterwards, Yoshi trained under Sho in martial arts so that he may defeat Shredder should he be resurrected, quickly becoming a master of it. However, Yoshi's sadness over his mother leaving him eventually turned to bitterness towards his own clan, leading him to disbelieve the existence of the Shredder. Then one day, as a teenager, Yoshi entered an argument with his grandfather, which led to him deciding to abandon his family duties so that he can pursue his dream of going to Hollywood to become a movie star.
Using the skills he was taught, Yoshi quickly rose to fame and fortune as the action star known as "Lou-Jitsu". Then one day, he was visited by Grandpa Sho, who demanded that Yoshi end his career so that he can come back home to fulfill his true destiny. However, Yoshi sternly refused one more time before closing his trailer's door in his face. Seeing that Yoshi has truly cut ties with his clan, the saddened Sho chose to respect his grandson's wish and left, never to speak to him again. Yoshi watched from the window as his grandfather walked away, slightly remorseful for he treated his former teacher.
Kidnapping and mutation
When shooting for a film, Yoshi met Big Mama, who drove his trailer, and the two started a romantic relationship. However, Yoshi was unaware that she is a Yōkai, despite some obvious signs. After attempting to propose to her, he was thrown into the Battle Nexus , where he triumphed over his opponents. Sometime later, Yoshi had sworn off of fighting in the Nexus and tried to resume a more peaceful lifestyle where he not harm any living creatures.
However, his fame in the Battle Nexus attracted the attention of Baron Draxum, who wished to use his DNA to mutate an army that would serve him. It was through this process that the Mad Dogs were mutated from ordinary reptiles, making Yoshi the biological father of their human genes. However, unwilling to watch innocent creatures be turned into monsters for Draxum's cause, Yoshi freed himself and destroyed Draxum's laboratory, causing Draxum to believe that the Mad Dogs had been killed in the fire. In the midst of his escape, Yoshi released Draxum's other test subjects and a rat bit his finger just after his exposure to the ooze, causing his mutation. He doesn't remember everything from his transformation into his current form.
Splinter remained unaware of his sons' contact with Draxum and the Foot Clan until the events of Shadow of Evil. Upon discovering evidence of the Foot Clan, he impersonated a teenager and managed to spy upon his enemies, discovering that they were reassembling the Kuroi Yōroi. Realizing that this foreboded the possible return of the Shredder, Splinter pretended to be a member of the Clan in order to take a piece of the armor. This attempt was thwarted by Draxum and, unwittingly, his sons. Upon escaping without the armor piece, Splinter promised to tell his sons "everything" and stated that they were "way behind" on their destiny.
