The cards that are returned are chosen when the effect resolves, so this effect does not target.
The effect which returns an opponent's monster(s) to the hand does not target. You select the monsters to return at resolution.
When this card is flipped, the effect is optional, so you can choose not to activate the effect and not return any monsters. However, if you choose to activate the effect, you must return at least 1 monster your opponent controls to the owner's hand.