The relationship could develop through shared experiences. For instance, Naruto and Tora could get lost in a mysterious part of the village that is filled with ancient ninja traps. As they work together to escape, they learn about each other's strengths and weaknesses. Tora might be small but is very agile, and Naruto has his brute strength and ninja skills. By relying on each other, their relationship becomes stronger and more meaningful.
If brought back by a necromancer, Tora could be more intelligent and have a deeper understanding of the ninja world. Since it has experienced death and resurrection, it might have insights into the spiritual side of things that normal cats don't. Tora could also be more aggressive in protecting the necromancer, seeing them as its savior. And perhaps it would have a new form of communication, not just the normal cat meows, but something more complex that can convey more detailed information to the necromancer.
Sasuke would probably be indifferent at first. He is more focused on his own goals of getting stronger. But if Tora somehow gets involved in a situation that affects Sasuke's plans or if Tora shows some useful skills, he might start to respect Naruto's decision to keep Tora. For example, if Tora helps them track an enemy ninja.
One common theme is friendship. Harry and Tora's relationship is often at the center, showing how they support and care for each other through different trials.
Overcoming differences is also prevalent. Given that they might be different in character or origin in the fanfiction universe, they often have to work through their differences to achieve a common goal, like saving their world or helping a friend in need.
I'm not sure if there specifically exists a 'Naruto has a Tora lemon fanfiction'. Fanfiction covers a vast range of ideas, but 'lemon' often refers to adult - themed content which is not appropriate in many contexts. There are lots of normal Naruto fanfictions out there, though.
In such a fanfiction, Naruto might first encounter Tora while on a mission in the village. He could use his kind-hearted nature to gain Tora's trust. For example, Naruto might share his food with Tora, which is a simple yet effective way to start a friendship. Then, they could go on little adventures together around the village, like exploring hidden corners or chasing after little critters.
One common theme is friendship. Ushio and Tora have a very special bond, and many fanfictions explore how this friendship grows and endures through different situations. Another theme is adventure. They often go on various quests in the original work, and fanfictions expand on these adventures.
Unique about Naruto Tora Lemon fanfiction could be the way it twists the normal Naruto narrative. In the original Naruto, Tora is just a cat that causes trouble. But in this fanfiction concept, the 'Lemon' part could transform Tora's role completely. It might give Tora a more sentient or important role in Naruto's life, perhaps in a romantic or emotional context that is not present in the original story. It could also introduce new settings or scenarios within the Naruto world that are centered around this new relationship between Naruto and Tora. But again, this is based on the assumption that such fanfiction exists and is not just a random combination of words.