Definitely Naruto. And among the Nara clan, Shikamaru is a must - have. He's intelligent and has a unique relationship with Naruto. Besides, Shikamaru's mother could be a character. She could be the one who takes care of Naruto in a more motherly way, showing him the warmth of a family. Also, the clan elders might be involved. They would have to make decisions regarding Naruto's adoption and his place within the clan.
Naruto is the central figure. In the Nara clan, Shikamaru would be a key character. He and Naruto could have many adventures together within the context of the Nara clan. Also, Ino could be involved in some way. Since she's friends with Shikamaru and has a connection to Naruto through the whole group of friends. And of course, the head of the Nara clan at that time would be an important character as they would have the final say in Naruto's adoption.