Well, Naruto is a really strong - willed character. So, at first he'd be really hurt. But then, he would probably try to figure out why his family has forgotten him. He might go on a journey to find answers, all the while dealing with the pain of this rejection. He could also be angry at his family for forgetting him so easily, especially considering all he's been through.
Naruto would probably be really hurt at first. He's always been someone who values his friends and to be forgotten on his birthday would sting. He might try to hide his disappointment though, putting on a brave face.
Initially, Naruto would be in shock. He'd try to talk to his friends like Sasuke or Sakura, but when they look at him with blank stares, it would break his heart. He would feel like an outsider in his own village. But then, his ninja spirit would kick in. He would start investigating. He might think it has something to do with a new enemy or some hidden plot. He'd be on a mission to not only get his friends and family to remember him but also to protect the village from whatever threat caused this forgetting in the first place.
At first, Naruto would likely be very confused and hurt. He has always craved family love and acceptance, so this sudden turn would be a huge blow. He might try to plead with his family, asking them to believe him and give him a chance to explain.
At first, Naruto might be shocked and heartbroken. He has always longed for family acceptance, so being banished by them would be a huge blow. He could feel betrayed and angry, especially if he doesn't understand the reasons behind it.
Naruto might initially be heartbroken. He's a character who values family and connection deeply, so rejection would hit him hard. He could go into a state of self - doubt, wondering what's wrong with him.
Well, one possibility is that the 'new' Naruto, who is actually the original Naruto in a different role, could change the course of events in the Hidden Leaf Village. Maybe he would approach missions and training in a completely new way, leading to different power-ups and relationships with his comrades.
In a 'naruto is in a au harem fanfic', aside from the obvious choices like Sakura and Hinata, characters like Temari could be in Naruto's harem. She's from another village and has a strong personality. Her presence would bring in an element of cross - village relations. Karui is also a possibility. She's feisty and has her own set of skills. And then there's Kurenai, the jonin. She could be an interesting addition to the harem, with her experience and calm demeanor.
Naruto may try to find out the reason why he is forgotten. He will start by reflecting on his own actions. Maybe he thinks he has done something wrong that made his family forget him. Then he will strive to correct it. At the same time, he might also seek help from his friends like Sasuke and Sakura, who always stand by him.