Itachi and you have been together since you where 2 and itachi 5. after being put on a battle field at at age 4 and seeing so much death itachi was looking for a reason to live in this world and you gave him that. that is when he meets you, another Uchiha. your father was Fugaku advisor letting Itachi meet you. After the first time he saw you, it melted his depression and he decided he would protect something so precious

Then one day when you are 10 and itachi is 13, itachi kills the Uchiha clan with Tobi, but right when Tobi goes to kill you Itachi steps forward

"Do not touch her" Itachi threaten Tobi

"How do you know you can trust her?" Tobi asks Itachi gripping your arm tightly as Itachi's Mangekyō Sharingan eyes are activated and looking at you, trying to read you "If she stays alive she will have to join the Akatsuki too" Tobi sighed not wanting to fight Itachi

all you can do is look at Itachi with your brand new sharingan eyes after witnessing Tobi kill your family

"I'll be responsible for her" Itachi told Tobi keeping his calm, stoic expression.

(Time skip 8 years. Itachi is 21 and you are 18)

Since that night Itachi has never left you out of his site, not once. even when you think you are alone Itachi is still watching from the shadows. Over the years Itachi trained you himself making sure you knew everything he did, in result made Pain choose you and Itachi for the most complicated missions. everyone in the Akatsuki knew not to touch you unless they wanted to deal with Itach's Tsukuyomi, but that doesn't mean they do not flirt when they thought Itachi isn't around