Ok, here goes: 1. Shisui was a member of Akatsuki. He was also a type of medium, or recruiter for other Uchiha. His mission was to recruit the stongest of Uchiha into Akatsuki. 2. Him being Itachi's best friend, and Itachi becoming incredibly strong in and incredibly short amount of time, asked if Itachi would like to join. Itachi, being the upstanding citizen of Konoha that he was, decided that it would be best if Shisui, his best friend, died. He didn't want Akatsuki to ruin any other Uchiha, or citizens of Konoha. 3. In doing so, Itachi was granted the Mangekyou. However, when Akatsuki had heard that their Uchiha recruiter had been slain, paid a little "visit" to Itachi. 4. What they told him, I don't know, but they threatened him in some way, and said that he needed to repay the debt. They told him that he needed to killl everyone in his village and join them. Apparently the thread worked, and Itachi did as he was told. 5. He left Sasuke alive though. Why? Because he knew that Sasuke would be overwhelmed with the knowledge that his brother had done what he had. But, the reason he was such a jerk to Sasuke about was because he was trying to motivate him. Itachi saw the potential of Sasuke and wanted him to get stronger, so that one day, they could confront the leader of Akatsuki together. 6. However, Itachi hadn't anticipated that the mangekyou would cause you to lose your sight...and that's where my theory ends. We haven't seen Akatsuki since then, and right now, this "Road to Sasuke" chapter is proving more and more interesting, so, as the chapter goes on, so will my theory. What do you guys think so far?