First, start with a basic oval shape. Then, add the iris and pupil. Next, sketch the eyelashes and eyebrows. Finally, add shading and highlights for depth.
First, start with the basic shape. Sketch an oval and then divide it into sections to define the iris and pupil. Pay attention to light and shadow for a realistic effect.
If Naruto had a Sharingan in fanfiction, it would drastically change the story. He could quickly copy enemy jutsus like Sasuke. His combat ability would skyrocket as he could predict movements better. Also, his relationships might change. For example, his bond with Sasuke could be different as they'd both have the Sharingan. It would also make his training with Kakashi more interesting as Kakashi could teach him unique Sharingan - related techniques.
He might gain enhanced perception abilities, which would be a huge boost to his combat skills. With the Sharingan, he could predict his opponents' moves more accurately.
One possibility could be through a forbidden jutsu experiment gone wrong. Maybe some rogue ninja was trying to create a super - powered being and Naruto ended up being the subject. The Sharingan was transplanted into him, but only one eye was successful.
In some fanfictions, he might obtain it through a powerful jutsu gone wrong that somehow fuses Uchiha DNA with his own. Maybe during a battle where he's exposed to some strange chakra energy related to the Sharingan.
A rogue Uchiha who has lost the use of one of his Sharingan eyes due to a failed experiment. He becomes jealous of the protagonist who has one working Sharingan eye and tries to take it for himself. He might use his remaining Sharingan powers in cruel and unexpected ways to try and defeat the protagonist.