Naruto would probably be really excited. He loves new and cool powers, and the Sharingan is one of the most powerful and mysterious in the Naruto universe. He'd likely be full of questions and eager to see what Hana can do with it.
A possible plot could be a time - travel scenario. Hana and Naruto are sent back in time to the era when the Sharingan was first created. They have to figure out how to get back to their own time while also dealing with the power struggles and conflicts of that era. Hana's Sharingan becomes a key factor in their survival, as they use it to outwit powerful enemies and make allies among the ancient clans.
He might be initially shocked. Naruto is used to thinking of Hana as an ally, so if she hurts him, it would be unexpected. He could immediately try to get some distance to assess the situation and figure out why she did it.
Hana could be an original character created for this fanfiction. Maybe she is a new ninja in the village who Naruto falls for, but she has a hidden agenda that ends up breaking his heart.
It's also possible that Hana is related to one of Naruto's friends. Maybe she's Kiba's sister or something. And because of her connection to Naruto's friend, Naruto feels responsible for her safety. So when she's in trouble, Naruto steps in to save her without hesitation.
Hana is likely a character who decides to take Naruto in as her own. She might be a ninja with her own set of skills and abilities.
In fanfiction, Naruto could get the Sharingan through a blood - related connection that is revealed later. For example, it could be discovered that he has some distant Uchiha ancestry that gets activated somehow. Maybe a powerful enemy's attack awakens this dormant Uchiha blood in him, and as a result, he develops the Sharingan. It could also be that a powerful sage or a new character uses their own unique powers to bestow the Sharingan upon Naruto for a specific purpose.
One great fanfiction could be about Kakashi using his Sharingan to train Naruto in a special jutsu. Maybe he shows Naruto how to better perceive an opponent's moves by using the Sharingan's ability to analyze. This could lead to Naruto developing a new and powerful technique that combines his own chakra control with the insights from the Sharingan.
One possible fanfiction could be about a young ninja who discovers he has a special connection to Madara's Sharingan. Maybe he inherits some of Madara's latent powers through a mysterious family link. This could lead to him being hunted by those who want to use his power for evil or by those who fear it.
One possible fanfiction could be where Ino, with her mind - related jutsu, teams up with someone who has the Sharingan. They could go on a mission together and the Sharingan user might help Ino enhance her perception abilities. For example, if Naruto somehow had the Sharingan (in this fanfic concept), he and Ino could face an enemy that uses illusions. Naruto's Sharingan would see through the illusions and Ino could then use her mind - control jutsu on the real enemy.
Their relationship could develop slowly. At first, it might be awkward as they are strangers in a way. But Naruto's friendly nature could break the ice. He might share stories about his adventures, which would intrigue Hana. Hana, in turn, could show Naruto the traditions of the Inuzuka clan. They would gradually become friends and then, as they see each other's good qualities more often, fall in love.