Geez, you guys:
Sometimes the stabbing of the first born of a woman that was pursued and had sex with gods, which also may have included the brother of the possible rope tying 23 together, and that later went on to become a divine entity through its legend, only to be destroyed by his sister and then become young Akira, and then Sekai borrowing Kaori's body is just the stabbing of the first born of a woman that was pursued and had sex with gods, which also may have included the brother of the possible rope tying 23 together, and that later went on to become a divine entity through its legend, only to be destroyed by his sister and then become young Akira, and then Sekai borrowing Kaori's body.
Geez. A regular wednesday right there.
Edit: Jokes aside, I also think it was just a random stabbing. Just like what happened to Miku's parents.