One great 'Tobi Obito x OC Fanfiction' is 'The Hidden Bond'. It has a really interesting plot where the OC has a unique connection with Obito that gradually unfolds throughout the story. The character development is well - done, especially for the OC as she starts off as a shy girl but grows into a strong kunoichi through her experiences with Obito.
Minato might also be a prominent character. As their teacher, he can influence the way Obito and Kakashi interact. In some fan fictions, he could be the one to help them resolve their differences or provide some crucial information about their past that changes their current situation.
Naruto would probably be one of the first to try and rescue Kakashi. He has a strong bond with Kakashi and would not stand by while his teacher is in danger.
One common theme is redemption. Since Obito has a dark past in the Naruto series, in many fanfictions, the OC helps him find a path to redemption. Another theme is love against all odds. Their relationship often has to overcome obstacles like Obito's loyalty to his original goals or differences in their villages.
One idea could be a story where Female Kakashi and Obito are on a mission together in a mysterious land filled with ancient magic. They have to rely on each other's skills to survive and in the process, they start to see each other in a new light.
One great Kakashi x Obito fanfiction is 'The Bonds We Share'. It delves deep into their relationship, exploring how their past experiences shape their interactions in a post - war Konoha. It shows their growth and how they come to understand each other on a deeper level.
One possible plot could be that Tobi kidnaps Kakashi to gain some valuable information. Maybe he wants to know about the Sharingan secrets Kakashi has. Tobi could hold Kakashi in a secret lair and try to interrogate him.
In this fanfiction, perhaps Kakashi and Tobi meet in a battle. Kakashi might initially be suspicious of Tobi's true identity. Tobi could be playing mind games with Kakashi, trying to throw him off his game.
Kakashi could use his Sharingan to analyze Obito's moves and find a weakness in his defenses. Since he has the Sharingan, he might be able to predict Obito's attacks and counter them effectively, eventually finding an opportunity to break free.
One popular 'kakashi in love with obito fanfic' is 'The Unspoken Bond' which delves deep into their relationship. It shows how Kakashi's feelings for Obito develop over time through various shared memories and new experiences they face together.