A love interest who breaks his heart multiple times. For example, if this person plays with his feelings, lies to him, or cheats on him, Percy could become cold - hearted as a form of self - protection. He would no longer trust easily and would close his heart to new relationships.
Maybe Percy has been through a great betrayal, like his closest friend turned on him for power. So he starts to close off his emotions to avoid being hurt again.
In some fanfiction, Percy might be depicted as cold - hearted, but it's often a departure from his canon character. Fanfic writers may do this for creative or plot - driven reasons. However, the real Percy is known for his loyalty and big heart.
In some fanfics, Naruto might be depicted as cold - hearted, but it goes against his canonical character. The original Naruto is known for his warm - heartedness, determination, and his ability to see the good in people. Fanfic authors may take creative liberties for various reasons like exploring different storylines or character arcs, but it's not a common or true - to - the - source representation of Naruto.
One possible plot could be that after losing many friends in a major battle, Naruto becomes disillusioned. He might start to see the world as a cruel place where strength is the only thing that matters. So he shuts off his emotions to avoid further pain, and becomes cold - hearted towards his former allies and enemies alike.
One reason could be that the writer wants to create conflict. By making Percy cold - hearted, they can set up situations where he has to overcome this new trait. Maybe it's a way to show how much he's changed due to some extreme event in the fanfiction's plot.
If Naruto becomes cold - hearted, his relationships with the villagers would change drastically. The villagers, who once saw him as a hero, would now be faced with a cold and unapproachable Naruto. Children who used to look up to him would be scared. His friends from the Akatsuki days, like Nagato, might even see this new Naruto as a threat. Overall, his relationships would go from being warm and friendly to cold and distant, filled with suspicion and unease.
In fanfic, a tragic backstory that was different from his original one could lead to Naruto being cold - hearted. Maybe if he had been abandoned by the whole village instead of just being shunned by some, he could grow up bitter and cold. Also, if he had to make really tough decisions that cost him a lot, like sacrificing friends for the greater good in the fanfic world, it might harden his heart.
There could be an old gardener who mentors Percy. The gardener might teach Percy all about the plants in the garden, their needs, and how to keep the garden thriving.