I think the villagers would be highly affected. They already had a complex relationship with Naruto. Now, if he becomes the boogie man, they would either be extremely afraid or try to find ways to get rid of him. His transformation would disrupt the already fragile peace in the village. And his friends like Iruka, who has always been a positive influence on Naruto, would be heartbroken to see Naruto in such a different and perhaps feared state. They would try their best to bring the old Naruto back.
His friends would be the most affected. For instance, Shikamaru, who is used to Naruto's normal self, would have to adjust to this new and somewhat spooky Naruto. He might have to come up with new strategies to deal with Naruto's new abilities and behavior.
The ninja academy students would be very affected. Naruto was always a bit of an inspiration to them, being a self - made powerful ninja. But if he becomes the boogie man, they would be terrified. This could change their perception of what it means to be a ninja. Also, Naruto's sensei, Kakashi, would have a big role to play. He would need to figure out what happened to Naruto and how to guide him. If Naruto starts using his new powers in the wrong way, Kakashi would be responsible for stopping him or helping him find a better path.
In this fanfiction, Naruto might use his new 'boogie man' status to play pranks on his friends in a more stealthy way. For example, he could use his newfound abilities to move around unseen and startle them at unexpected moments.
Batman would definitely be one of the most affected. He's used to dealing with normal threats in Gotham, and Naruto's supernatural abilities would be a huge challenge. Another would be the Flash. Naruto's clones could potentially surround and confuse the Flash. Wonder Woman too. She's a warrior, but Naruto's unorthodox fighting style and his array of jutsu would be difficult for her to counter immediately.
His friends would be the most affected. People like Sakura and Kakashi who know Naruto well. Sakura is used to Naruto's kind - hearted and determined self. If he starts acting like Grimmjow, she'd be very confused and worried.
His relationships would change a lot. With Sasuke, he might be more of a distant observer rather than a passionate pursuer. With Sakura, he may not be as openly affectionate and more like a guiding figure. And with his other friends, he would probably keep a bit more distance, like Kakashi does, but still be there when they really need him.
Sasuke would be one of the most affected. He and Naruto had a complex relationship, from being rivals to friends. Naruto's death would leave a huge void in Sasuke's life. Also, Hinata. She loves Naruto deeply, and losing him would be devastating for her.
The Akatsuki would be highly affected. Since Naruto has future knowledge, he could stop their plans before they even start. Also, his friends like Sasuke would be affected as Naruto could prevent Sasuke from going down the wrong path.
He could become more protective. Since Kiva's powers are powerful, Naruto might feel a greater sense of responsibility to protect his village and friends. He might also be more secretive about his new powers, at least until he fully understands them. And his sense of humor might change a bit, becoming a bit darker or more sarcastic as he gets used to his new identity as someone with Kiva - like abilities.
Naruto's personality might still shine through even as an Arrancar. He's always been determined and kind - hearted. However, he could become a bit more solitary at first as he adjusts to his new form and powers. The Arrancar nature might make him more cautious in some ways, but his basic values of friendship and protecting the weak would remain. He might also develop a bit of an edge, as Arrancars are often seen as more menacing, but it would be a surface change. Deep down, he'd still be the Naruto who wants to bring peace and joy to his village.
The Naruto universe would be in for some chaos. Gaara's new obsession could disrupt the balance of power dynamics. If he starts to prioritize the fanfiction - related ideas about Sakura over his duties in the Sand Village, it could lead to political unrest or at least some tension between the Sand and Konoha. After all, his actions as a leader are important for maintaining peace between the villages.
Well, it could be that the author took the concept of Naruto and twisted it to make him into the 'boogie man'. Maybe Naruto has some dark power or is involved in some spooky events. It could be a really interesting take on the Naruto character, exploring a side of him that is far from the usual heroic image we have of him. For example, he might be seen as a threat by the villagers in this fanfiction, instead of a hero like in the original series.