Well, perhaps the story could be about the daughter discovering her own unique abilities that are different from Kakashi's. This could lead to some interesting father - daughter bonding moments as he tries to help her develop those powers. Also, there could be a plotline where the daughter gets involved in a mission that is related to Kakashi's past, and they have to work together to solve it.
In this fanfiction, a possible plotline is that the oc daughter is initially not accepted by the village because she is an 'oc' (original character). Kakashi then has to fight for her acceptance. Along the way, she befriends other ninja kids and they go on small adventures together. As she grows older, she may face a big challenge that forces Kakashi to make a difficult decision between protecting the village and saving his daughter.
It could be an original character created just for the fanfiction. Maybe a mysterious ninja woman who crossed paths with Kakashi during a mission and they had a brief but intense relationship.
A plotline could revolve around Sakura getting special training from Kakashi. He could pass on his unique skills and knowledge, like his lightning - style jutsu or his stealth techniques. This would make Sakura an even more formidable ninja and also strengthen their father - daughter bond.
One possible plotline could be that the oc with the evil quirk tries to hide it from others at first. They might be afraid of being ostracized. For example, they could pretend to have a normal quirk in public but struggle internally with the dark impulses their evil quirk brings. Another plotline could involve the oc being forced to use their evil quirk for self - defense in a dangerous situation and then having to deal with the consequences of others seeing what they can really do. Maybe they get hunted down by heroes who misinterpret their actions as villainous.
One plotline could be that they face difficulties during the pregnancy due to their ninja duties. Maybe they have to hide their pregnancy from enemies or deal with the physical strain of being a ninja while pregnant.
A possible plotline could be that a new enemy targets Kakashi because of his distinct face features, believing there is some hidden power in his appearance. Naruto then has to protect Kakashi. Another plotline could be a magical spell that gets cast on Kakashi's face, changing his expressions uncontrollably, and Naruto tries to find a way to break the spell.
Perhaps there's a mission where Kakashi and Sasuke are on opposite sides. Kakashi is following the orders of the village, and Sasuke is following his own path for revenge. In a confrontation, Kakashi uses his Sharingan - based techniques against Sasuke. Sasuke, not fully prepared to face Kakashi at that level, gets hurt. This would add more complexity to their relationship as teacher and student.
A storyline might involve the OC daughter being trained by Itachi in the ways of the ninja, and she becomes a prodigy. As she grows, she might face challenges in the form of rival ninja who are jealous of her skills or her connection to Itachi. Also, there could be a story where she tries to reunite Itachi with Sasuke in a more peaceful way than in the original Naruto story.
One possible plotline could be that Kakashi is in a life - threatening situation during a battle against a powerful enemy. Naruto, seeing no other way to save him, uses a powerful and self - sacrificing jutsu that costs him his life. Another plotline might involve Naruto making a deal with some dark force to save Kakashi, but the price is his own life. Or perhaps in a mission gone wrong, Naruto takes a fatal blow meant for Kakashi.
One possible plotline could be them dealing with the challenges of Kakashi's ninja duties while maintaining a marriage. Another could be Rin adjusting to life in Kakashi's village.
One possible plotline could be them dealing with the unexpected pregnancy in the middle of their ninja duties. They might have to balance their responsibilities to the village with preparing for a new life. Another could be the reactions of their friends and comrades in the village. For example, how Naruto or Tsunade would react to the news.