Perhaps in this fanfiction, there is a hidden backstory where Grimmjow had an adventure in a world similar to Naruto's. He could have had a relationship with a woman there who had some sort of special power or connection. This relationship then led to the birth of Naruto. It might also be that some sort of genetic or magical experimentation was involved that combined their DNA in an unexpected way.
In the fanfiction, it could be that the concept of family and lineage is completely reimagined. Maybe in this fictional world, the idea of a son doesn't have to be a traditional biological one. Naruto could be 'Grimmjow's son' in the sense that Grimmjow took him under his wing and mentored him in a way that was so profound that it was considered a father - son relationship. And over time, through some magical or otherworldly means, they actually became related on a more fundamental level.
Well, in fanfiction, the author can bend the rules of the original universes. Maybe it could be justified through some sort of time - traveling magic. For example, Sherlock could be from a future time where magic and Muggle worlds have merged in some strange way, and Harry Potter, through his powerful magic, was able to travel back in time and have a relationship that led to Sherlock being born. It's all about the creativity of the fanfiction writer.
One possible way is if Aphrodite, in the context of this fanfiction, represents a force that Naruto sees as having corrupted his family or his ninja way. Maybe Aphrodite's ideas about love and beauty conflict with the values Naruto has been taught in the ninja world, like loyalty and self - sacrifice. So he could develop a hatred towards her for what he perceives as her negative influence on his family.
In this fanfiction, Naruto might inherit Grimmjow's ability to adapt quickly in combat situations. Grimmjow was known for his improvisation during battles, and Naruto could have that same skill. Also, Grimmjow's sense of loyalty, though in a different way than Naruto's original loyalty, could be passed on. While Naruto was loyal to his friends and village, he might have a more primal and individualistic loyalty similar to Grimmjow's loyalty to his own kind or those he respects.
Grimmjow's high - speed movement would be a great asset in the Naruto world. He could outpace many ninjas. His reiatsu - based attacks could be seen as a new form of energy - based jutsu. For example, his Cero could be like a super - powered ninjutsu blast. His ability to regenerate quickly would also give him an edge in battles against ninjas who don't have such a power.
In the fanfiction, Naruto could justify his hatred because he may have grown up seeing other kids with their mothers. Kushina's absence during his formative years could have made him feel unloved and unwanted. He might think that she chose to leave him, not considering how much he would suffer, and thus hatred could develop.
Well, it could be a case of Voldemort possessing a relative of Hermione's in the past and through that connection, a sort of 'daughter - like' bond was created. Fanfiction often plays with these wild and dark ideas. It might also be that there was a deal made between Hermione's ancestors and Voldemort (or his predecessors in the dark arts) that had unforeseen consequences generations later, resulting in Hermione being considered his daughter in this fictional scenario.
One way to justify it could be through a series of betrayals. Maybe Naruto discovers that Konoha has been using him all along, and his family has some dark secrets that make him feel betrayed. For example, if he finds out that his father was involved in some unethical experiments that led to the suffering of many villagers, that could turn him against both Konoha and his family.
One way could be that Naruto is an orphan found by someone else entirely. Maybe he's taken in by a group of traveling merchants who raise him. His skills and abilities could be developed through different means, like learning from the various people he meets during his travels with the merchants.
One possible plot could be that Naruto, after being exposed to some strange chakra or magic, starts to take on Grimmjow's aggressive and fearless attitude. He might become more impulsive in battle, like Grimmjow, and start to challenge his enemies without much thought for strategy at first. His friends would be confused by this sudden change in his behavior.
One way this could work is through shared values. Naruto is known for his never - give - up attitude and his strong sense of loyalty. Artemis, often portrayed as a strong - willed character, could be drawn to these qualities. Maybe in a crossover universe, they meet during a battle against a common enemy. Naruto's determination in the face of danger could impress Artemis, and she might start to see him in a different light, gradually falling in love as they fight side by side.