One idea could be that Black Widow is somehow transported to the Naruto universe. She teams up with Naruto on a mission. In the middle of their journey, they come across a magical lemon - shaped object that gives them unique powers for a short time. This leads to them having to learn to work together even more closely while dealing with the strange side - effects of the new powers.
Maybe in a fanfiction, Black Widow is a spy sent to the Naruto world to gather intel on a new threat that could potentially cross over to her own universe. She meets Naruto, who is initially skeptical of her. They find a lemon grove that has been corrupted by dark chakra. To purify it, they have to combine their skills. Naruto uses his Rasengan and Black Widow uses her combat expertise, and in the process, they start to respect and trust each other more.
I'm not sure if there is a specific 'Black Widow' and 'Spiderman' crossover fanfic that involves 'lemons'. Fanfics can cover a wide variety of themes and combinations, but the 'lemon' aspect often implies some sort of adult or inappropriate content. There are many fanfic platforms out there, but it might be difficult to find one that combines these two superheroes in that way due to the nature of the 'lemon' concept.
One idea could be that Naruto somehow ends up in the world of Fullmetal Alchemist and his chakra-based attacks are mistaken for some form of alchemical explosions. For example, his Rasengan could be seen as a condensed form of alchemical energy that explodes on impact.
Perhaps in a fanfiction, a character has a special power related to growth. They accidentally use this power on a lemon they just ate, and it starts growing uncontrollably in their stomach. This could cause them to have strange cravings or even gain new abilities due to the energy of the growing lemon. The story could then focus on how they control this new situation and what they do with their new - found situation.
There could potentially be some 'Black Widow Hulk' fanfic with what might be considered 'lemon' aspects out there in the vast expanse of the internet. However, such content might be difficult to find as it may not be promoted on major fanfic platforms due to content policies. Major platforms usually focus on more family - friendly or at least non - explicit content. So, if it exists, it's likely in some of the more niche or less - regulated corners of the fanfic world.
One possible plot could be that Naruto is somehow transported to the underworld. There, he meets a powerful underworld character who has a grudge against Konoha. But Naruto, with his determination, tries to make peace. Along the way, he discovers a new form of chakra related to the underworld's energy. And as for the 'lemon' aspect, perhaps there could be a budding romance between Naruto and a female underworld dweller where they share some tender, romantic moments.
One possible plot could be that Naruto, with his godlike powers, enters a crossover world. He might meet characters from another universe and use his skills to solve problems there. For example, if it's a crossover with a magical world, Naruto could use his chakra in new and unexpected ways to fight against dark magic. His 'godlike' status would give him an edge, allowing him to adapt quickly and form alliances with different characters.
One possible plotline could be that Black Widow somehow gets transported to the Naruto universe. She could use her combat skills and spy training to help the ninja in Naruto's world with a particular mission, like dealing with a new and dangerous enemy that has techniques similar to those in the Marvel world. For example, an enemy that can control minds like some villains in the Marvel universe.
Well, perhaps there is a plot where a powerful artifact has the ability to merge different universes. Naruto's and Black Widow's worlds start to blend. They are brought together by this strange phenomenon. At first, they are suspicious of each other. But as they discover that they are both after the same goal, which is to stop the artifact from causing more chaos and destruction, they start to cooperate. Their combined skills of ninjutsu and spycraft prove to be a formidable force against the various threats that emerge during this strange event.
It could involve Naruto being transported to the Marvel universe. He would be this strange, new kind of being with his chakra powers. Black Widow would be intrigued by him, and they might start off as allies. As they work together, a romantic connection could develop over time as they learn about each other's pasts and what they've been through.
A plot could involve Goku Black arriving in the Naruto world during a time of great unrest, like when the Akatsuki is causing chaos. He sees the shinobi as weaklings compared to his Saiyan strength. However, Naruto, with his Sage Mode and Nine - Tails chakra, manages to hold his ground against Goku Black in a first encounter. This catches Goku Black's attention, and he decides to study these 'new' powers. Meanwhile, the shinobi villages must decide whether to see Goku Black as a potential threat or an opportunity to learn from his power. Eventually, they could team up to fight a greater evil that emerges due to Goku Black's presence in their world.