[This chapter is free and does not charge anything.]
There are many fan-created interpretations of Uchiha Shisui's age and promotion timeline.
But in fact, the official material has already established Uchiha Shisui's experiences.
In the official novel Itachi's Story, the Third Shinobi World War had ended, which was the time period covered in the previous chapter of this book.
Itachi was four years old.
Uchiha Shisui was still only a Genin.
However, during this experience of being "rescued," he awakened the Mangekyō Sharingan because a Genin on his team and close friend died.
Itachi was five years old when the Nine-Tails' Rampage occurred.
Afterward, Uchiha Shisui found five-year-old Itachi and became acquainted with him.
The reason was the knot in his heart over having caused his friend's death.
The hand that should have reached out never did, because Uchiha Shisui was jealous of that friend.
He had watched helplessly as his close friend was killed by the enemy.
These are the established details in Hokage Ninja.
Manga → Novel → TV anime
This is how most adaptations proceed.
Many of the TV anime episodes we watched were actually already "third-hand" adaptations.
A lot of things were drastically altered based on the "multiple officially published novels."
For example, in the manga,
Uchiha Fugaku did not have the Mangekyō Sharingan.
In the Itachi's Story novel,
Uchiha Fugaku did not have the Mangekyō Sharingan either.
In the TV anime adapted from the novel, Uchiha Fugaku was drastically rewritten to possess the Mangekyō Sharingan.
In the end, it was completely useless.
Because it inevitably conflicted with the manga and novel plots, there was no way to use it, and the story could not justify itself.
There are many instances in the TV anime where the writers dared to drastically alter the settings but did