If there are face-up monsters with the same name on the field, destroy those monsters. (If a monster is Summoned or flipped-face up that has the same name as a monster that is already face-up on the field, the new face-up monster is destroyed. If they are Summoned or flipped face-up at the same time, they are all destroyed.)
As long as this card remains face-up on the field, more than 1 monster with the same name cannot exist face-up on the field. If a monster with the same name as a face-up monster on the field is Normal Summoned, Flip Summoned, Special Summoned or flipped face-up later, it is destroyed. (If monsters with the same name are Summoned or flipped face-up at the same time, they are all destroyed.)