It might be. Since both Naruto and Attack on Titan have huge fan bases, a fanfiction like this can attract a lot of attention. The idea of Naruto, with his unique abilities, stepping into the world of Attack on Titan to save Eren's mom is full of potential for creative and exciting storylines. For example, Naruto could use his shadow clone jutsu to deal with the Titans while trying to reach Eren's mom in time.
Percy might become more independent. Without his mom's presence, he has to rely more on himself. He could start to take on more leadership roles within the demigod community. He also may develop a darker side to his personality, as the pain of his mom's death lingers. However, through his experiences and the support of his friends, he gradually learns to balance this new, harsher side with his original kind - hearted nature.
Maybe Naruto somehow gets transported to the Attack on Titan world. He quickly realizes the danger that Eren's mom is in. Using his ninja skills, he battles the Titans and manages to rescue her just in time. After that, he might try to find a way back to his own world while also getting involved in the local affairs of the Attack on Titan world.
The exploration of power dynamics is also common. Eren was a very powerful figure. With his death, there is a power vacuum. The fanfic might explore how different groups or individuals try to fill this void. Some might try to take on his role, while others might oppose the idea of having a single dominant power like Eren had, leading to conflicts and power struggles within the story.
Another theme is growth. After his mom's death, Percy often has to grow up faster and become more independent. Fanfics might show him taking on more responsibilities and maturing in ways he wouldn't have if his mom was still alive. For example, he may become more decisive in battles or in dealing with other challenges. In some fanfics, there's also the theme of legacy. Percy might discover things about his mom that she left behind for him, like a hidden power or a special message. This gives him something to hold on to and also adds to the idea that his mom's influence still lives on even though she's gone.
One possible plotline could be Percy's journey of grief and how he copes with the loss. He might become more withdrawn at first, then gradually find strength in his friends and his quest. Another could be his search for a way to bring his mom back, perhaps delving into dangerous magic or making deals with powerful beings. Maybe he also has to face the fact that his mom's death was part of a larger plan by the villains and he has to stop them from achieving their ultimate goal.
Percy often becomes more somber. He may lose some of his initial naivete. For instance, he might be more cautious in his actions, thinking twice before jumping into a fight like he used to.
There could be a fanfiction titled 'Percy's Struggle After Losing His Mom'. In this, it could show Percy having flashbacks of his mom during battles or difficult times, and how those memories both haunt him and give him the will to keep going. It might also include how he tries to honor his mom's memory in different ways.
One 'percy's mom dies fanfic' that might be touching is 'A Mother's Legacy'. It delves deep into Percy's grief and how he copes with the loss, showing his journey of self - discovery after such a tragic event.