Satoru Gojo is designated as the strongest sorcerer due to his broken technique called ‘limitless’ and his special ‘six eyes’. Even though since birth Gojo was destined to be the strongest and most influential sorcerer and had these powerful blessings, he wasn’t always considered to be the strongest, it was one certain mission during the hidden inventory arc that made Gojo what he is today.
Suguro Geto, his only best friend, was the one person who seemed to be right next to Satoru Gojo in the race of becoming the strongest sorcerer. Geto is the master of technique curse manipulation authorizing him to capture any curse and employ it in a fight. They had contrasting outlooks, Geto fancied safeguarding the weak as he believed it was his duty as strong to do so while Gojo was convinced by the fact that it was destined for weaklings to decline.
But this very incident changed everything, henceforth switching their dynamics, paving the way for Satoru Gojo to become who he is today along with Suguro Geto to become the most dangerous curse user that the Jujutsu world had ever seen.
In the second year of school, Gojo and Geto were assigned a mission by Master Tengen to secure the star plasma vessel. Weighing up Master Tengen, he is an immortal jujutsu sorcerer who resides within the tomb of the star corridor, the barrier that protects Jujutsu high schools, as described by Principal Yaga. He has the curse technique of immortality, which will try to ascend his body once he’ll age and causes him to evolve into something more than a human and may cause the destruction of the world.
Hence, every 500 years he has to combine with a star corridor vessel, a person who is compatible with Tengen’s technique to revive his body information and keep the barrier in Japan stable. But those who choose to worship him like the time vessel association believe that his evolution is necessary as his merger with the impure human vessel is wrong. Thus, they would do whatever it takes to prevent the merger.
During the mission, Gojo and Geto formed a bond with the star vessel, Riko Amani, and felt that she had a right to live her own life not just as a vessel but Riko herself. They respected Riko’s choice. This made a huge impact on the boys, shaping their future. While they were escorting her, the time vessel association hired Toji, the sorcerer-killer, to kill the vessel. Toji Fushiguro had made his name in the jujutsu world as one of the most elite assassins, due to his ability where he can assassinate the target undetected as he was able to move through barriers because of no cursed energy.
Toji planned to scrupulously wear Gojo down using bounty hunters, he employed to kill Riko as bait, and then make a sneak attack. By just being extremely quick, fierce, smart, and strong he literally decimated Satoru Gojo and does pretty much the exact same thing with Geto. After putting both Gojo and Geto down he killed Riko and took her body to the association, to get his money. He added, “With all your blessings you lost to a monkey-like me who can’t even use Jujutsu”.
During this near-death experience, Satoru Gojo was able to find the core of cursed energy and unlock his true strength. He killed Toji with no struggle and set off to practice his limitless and six eyes.
Then only Geto started to feel inferior to him and diverted his path. He started to think that non-sorcerers are quite unappreciative of what the sorcerers do and decided to butcher them. He asked Gojo, “Are you strongest because you’re Satoru Gojo, or are you Satoru Gojo because you’re the strongest”. This made Gojo examine himself as a jujutsu sorcerer and set himself up to change the world. This is how he became the Saturo Gojo we know today.