Bleach, Vol. 6

Ichigo Kurosaki may not know this, but the world he lives in is one predicated on balance between the living and the dead, between everyday life and the Soul Society. Soul Reapers aren't merely fighting Hollows; they are charged with the grand task of equalizing the balance between this life and the next.

Naturally, if too much energy is channeled to one side, really bad things will happen - just as they're happening now! Ichigo and Uryu's competition inadvertently results in generating a leviathan of a Hollow whose sheer size is capable of tearing the Soul Reaper's delicately constructed balance to ribbons.