If "Hyper Hammerhead" attacks "Des Kangaroo" in Defense Position, their effects form a chain; "Hyper Hammerhead" is Step 1 because it is the turn player's effect, and "Des Kangaroo" is Step 2. "Des Kangaroo" resolves first and destroys "Hyper Hammerhead", then "Hyper Hammerhead" resolves and "Des Kangaroo" is returned to the owner's hand.