When Nightmare Pain and 1+ Yubel monsters are on the field, the controller of Nightmare Pain does NOT choose the attack targets, the opponent chooses which Yubel monsters they attack, though they MUST attack Yubel monsters still.
When Nightmare Pain and 1+ Yubel monsters are on the field, the controller of Nightmare Pain does NOT choose the attack targets, the opponent chooses which Yubel monsters they attack, though they MUST attack Yubel monsters still.