I recently was playing in an edh deck and my opponent has a sen's triplets in play and played approach of the second sun from my hand. On a later turn, he managed to play it again. Does this cause him to win the game?
While it is true that your opponent has "cast another spell named Approach of the Second Sun" this turn game, that player did not cast this Approach of the Second Sun from their own hand. The first check is false.