Well, in some fanfics, he might obtain them through some ancient ninja magic. Maybe he discovers a hidden scroll or a long - lost temple that grants him the power of all doujutsu.
The 'naruto doujutsu fanfic' is interesting because it allows for a lot of creativity. Doujutsu in the Naruto series are already very cool, and in fanfics, authors can create new types, powers, and backstories for them. For example, they can explore what would happen if a character had a doujutsu that could control time. It also gives a chance to expand on the existing Naruto world and characters, like seeing how Naruto or Sasuke would react to a new doujutsu user.
One implication is that he becomes extremely powerful. He would be able to see things others can't, predict attacks more accurately, and have a greater variety of combat techniques at his disposal.
Another might be the Byakugan. It gives a wide - range view and can see the chakra points in the body. In fanfiction, new and unique abilities of these doujutsu can be explored. For example, the author might create a situation where the Sharingan can not only copy physical techniques but also mental jutsus.
One possible doujutsu could be a time - manipulating doujutsu. It allows the user to slow down or speed up time in a small area, giving them an edge in battles. Another could be a soul - reading doujutsu, which enables the user to see the true intentions and past experiences of others by looking into their souls.
In the fanfiction, it could be that Naruto inherits the doujutsu. There might be a hidden lineage that Naruto is a part of, and when the time is right, the doujutsu awakens within him. This could be related to his Uzumaki heritage, which has many secrets yet to be fully explored. It's possible that some long - lost relative had this doujutsu and it has been passed down through the generations, finally emerging in Naruto.
The doujutsu can drive the plot by giving characters unique powers. For example, if a character has a powerful doujutsu, it can make them a target for other characters who want to either steal the power or use it for their own purposes.
One great 'naruto doujutsu fanfic' is 'The Doujutsu's Ascent'. It focuses on a character developing a new and powerful doujutsu ability. Another one is 'Doujutsu Unleashed' which has amazing battles involving different doujutsu users. And 'Mysteries of the Doujutsu' is also a good read as it delves deep into the lore behind the doujutsu in the Naruto universe.
There's a fanfic where Naruto's eye doujutsu is related to time - control. It allows him to see different timelines and predict his opponents' moves. This makes for some really interesting battles as he outsmarts his enemies in ways he couldn't before. The story also delves into how this power affects his relationships with his friends and the village.
The main character could be an original character with a special doujutsu. For the harem part, characters like Sakura, Hinata, and Ino could be part of it. Sakura with her strong medical and combat skills, Hinata with her gentle yet powerful Byakugan abilities, and Ino with her mind - control jutsu would make for an interesting dynamic around the main character with the doujutsu.