The Strawberry's Rebellion

When Kronos won the Second Titanomachy and assumed his divine form to recreate the world in his own image, he weakened the barrier separating dimensions. Meanwhile, during the Second Winter War, to counter Ichigo's Final Getsuga Tenshō, Aizen trapped Ichigo in a Caja Negación. Only, the weakened barrier between dimensions coupled with Ichigo's attack transported him to a new world.