Star-vader, Chaos Breaker Crisis

:[ 1‐card with "Star-vader" in its card name] When this unit is placed on , or when your G unit with "Star-vader" in its original card name , you may pay the cost. If you do, your opponent chooses one of his or her rear-guards, and locks it. :When your opponent's locked card is unlocked, if a unit was not retired due to the effect of this card during this turn, you may retire that unlocked unit. If you do, draw a card.