A more complex plot could be centered around any potential threats to Rin during her pregnancy. There could be enemies who see this as an opportunity to target them, so Kakashi has to be extra vigilant in protecting her. This could lead to some intense action scenes where Kakashi uses his Sharingan to fend off attackers while also ensuring Rin's safety.
One plot idea could be that the OC is a ninja from another village who has a secret relationship with Kakashi. When she becomes pregnant, she has to decide whether to stay in her village or try to be with Kakashi in Konoha. This could create a lot of tension and drama, especially with the political implications between the two villages.
One idea could be exploring how the pregnancy changes their relationship dynamic. Sesshomaru, who is usually stoic, might become more protective and caring. Another plot could involve the challenges they face from the demon world due to this unexpected pregnancy. Maybe other demons see it as a sign of weakness or an opportunity to gain power. Also, Rin's growth as she prepares to become a mother in a world full of danger could be an interesting aspect to write about.
A possible plot is that Obito and Rin are living in a peaceful village when Rin finds out she is pregnant. They then start to plan for their future as a family. However, rumors start to spread in the village that the baby might have some special powers. This causes some unrest among the villagers. Obito and Rin have to work together to convince the villagers that their baby is just a normal child and that they only want a peaceful family life.
One idea could be that they face challenges in their ninja duties while being pregnant. For example, they have to deal with enemies who might target them because of their vulnerable state. Another could be the support they get from their friends and the village. Their friends could help them with things like getting proper medical care and protection.
One idea could be that Kakashi travels back to the moment right before Obito's 'death'. He uses his knowledge of future events to prevent the cave from collapsing on Obito. Then, together they are able to rescue Rin more effectively and change the whole tragic course of events.
One idea could be exploring Kakashi's relationships within the Anbu. For example, his friendships or rivalries with other members. Maybe there was a particular mission where he had to rely on a teammate he didn't trust at first.
A great plot could be a crossover where Sesshomaru and Rin end up in a magical realm that is a mix of their two worlds. Here, they meet new characters who mistake them for powerful beings from their own lore. They have to work together to find a way back home while also dealing with the power struggles in this new realm. Or perhaps a plot where Rin gains some of Sesshomaru's powers accidentally and Sesshomaru has to train her to control them, which leads to a deeper bond between them as they face challenges from other demons who are envious of Rin's newfound powers.
Well, a cool plot could be that there is a mysterious force that links Naruto and Rin across different dimensions. Naruto discovers this connection and tries to find Rin in another dimension. As he does, they both realize that they have a shared destiny to save both their dimensions from a common threat. Maybe it's an ancient evil that was once sealed away but is now breaking free.
One idea could be that Rin, with her medical skills, tries to save Kakashi but fails due to some unforeseen circumstances. Maybe an enemy uses a powerful jutsu that she can't counter in time. This would be a tragic twist, as her being alive doesn't change the outcome for Kakashi.
One plot idea could be Minato discovers Kakashi's hidden potential as a baby. Maybe he has a special chakra signature that Minato realizes can be harnessed for great things in the future. Another could be Minato taking on a father - like role to baby Kakashi, teaching him basic ninja skills early on.