You were an oprhan of the Uchiha clan and you were away during the massacre. Nobody really knew you were an Uchiha and assumed Sasuke is the last one.

After you went trough the genin exams you were placed on a genin team with a jounin leader to go on missions with.

One day on your mission you encountered Orochimaru. He knew you were an Uchiha and since you were out of the village this whas the fastest wat of getting his hands on a Sharingan. It whas mostly the Jounin figthing him but he got easily outpowered and died. You and your genin team started running but to no avail, he whas picking you out one by one untill only you were left but by that time you were too close to the village so he had to drop it. When you got back the first thing you did whas report to Hiruzen, the current Hokage about it but really he had too much work to deal with Orochimaru and put it on hold due to the upcoming Chunin exams but he took pity on you and let you go in them solo

But seeing your friends die infront of you had took a huge blow on your mental healthand you awakened the Mangekyou sharingan

It whas time for the Chunin exams, everything whas going well untill the second round where you once again encountered Orochimaru who whas figthing Sasuke Naruto and Sakura because he knew you'd be stronger do to your Mangekyou and having no etammates to worry about but you however were too afraid to join the fight and ran away to look for the second scroll you needed somewhere else. When you found them you instantly went to turn them in not even wanting to think about running into Orochimaru

During the third round you kept your Sharingan hidden to make sure nobody knew and you passed without it. It whas during the month for training that you used it, trying to perform Amaterasu but unluckly for you, Kakashi whas currently nearby and saw it but instantly had an investigation launched on you: the results find out you were directly related to Madara Uchiha and were a product of artificial sementation but you had no idea