Itachi was 14 years old, when he killed his own clan and ran away and joined Akatsuki. He did this all for betterment, but obviously he's a villain in everyone eyes. They both were good friends back then, in love with each other secretly, but could never confess. Itachi was in love with you, his feeling never changed. Even after years of being away from her, his heart is still stuck at the same girl.