Uh

i believe that ai and tsubaki committed suicide and aoi was killed by kikyou; but to be fair, i also am unsure why ai and tsubaki decided to make this decision and i need answers :<

Tsubaki was going to stab Aoi, but Ai ran in front to stop him from becoming a murderer. She was (accidently) stabbed fatally by Tsubaki. As Ai is dying, they repeat their promise to be together forever and Tsubaki ties their hands together so they won't get separated, then they jump into the river and drown.