Disclaimer: Naruto is not mine
For this prompt:
What if Itachi were an only child? - Life without Sasuke. What would it have been like?Itachi has no friends
Mikoto goes back to work when Itachi is 5 after taking weeks off. He is old enough to go to the academy now. "Tadaima." He always announces his return, but there is no cooing of a baby brother and no mother cooking in the kitchen. Shisui does not come over to babysit Sasuke, Shisui is a cousin, some distant dark-haired, dark-eyed face in a clan of hundreds.
There is no back up heir, Itachi makes genin at 6 and chunin at 7. He is more than a prodigy, he is inhuman. There is no brother to tuck in at night and no mother at home to act as a buffer. The Hokage forbids Itachi from taking the jonin exams until he is 13. His father talks about how the Hokage is holding him back. He is promoted to jonin on the field at 9 by some ANBU who must not have known.
Itachi does not care for his teammates.
Hatake Kakashi dies when Itachi is 9. Itachi steps over his superior's squirming body to retrieve the scroll. He is a liability, a broken weapon, he will hold Itachi back and he can tell their enemies too much. He snaps the almost too frail skin, it's been sheltered the mask and it feels like a child's. He takes Obito's eye back to Konoha, it may prove to be useful.
Itachi is the perfect shinobi, he gives his report calmly, neatly, efficiently. He stands before the Hokage's desk and tells of too many enemies. He speaks of Kotetsu - incautious, an insignificant loss, Kakashi - more significant, but overall it balances out in Konoha's favour.
The Sandaime hears all of Itachi's reports in person, he rarely questions the blank child who is everything a shinobi should and shouldn't be. The word Root is bandied about, but Danzo has had no hand in making this monster, this is a child of the Uchiha's making.
Itachi has no friends
He is shown the Uchiha vaults beneath the temple. He thinks nothing of the desecration of somewhere that was supposed to be a place of peace. He understands the implicit message in his father showing him these scrolls. Itachi should get stronger, Itachi should gain this extra power. Itachi does not know who to kill. Someone who wouldn't be noticed, or someone who could be explained.
Itachi hasn't been touched with anything other than violence since he was two. Itachi has a good memory. He finds his mother just home from a mission and sleeping. She wakes, she is a jonin, she does not even beg for mercy as he stands over her. He makes it quick, he is efficient. She collapses to the bed which quickly turns red beneath her.
Itachi is not supposed to be in Konoha, her body is left on the bed to bloat. No one enters their home until they return, the adults all know what has happened and the children can't recognise the scent of decaying flesh. Itachi touches the raised bump of her stomach with a soft, light hand.
There are witnesses and the Hokage knows Itachi can't be faking the surprise. Itachi stands and cries for the first time since he was one, but it's okay, because he's acting, he thinks. It is easy to pretend that he can feel a child move inside the womb. She is more a mother in death than she ever was in life.
His father says nothing at the sight of his dead wife. Itachi becomes more the Uchiha they have always wanted him to be and the Uchiha cower from him more than ever, which is okay, because Itachi does not need friends.