To search (探す sagasu) a hidden zone, typically the deck, is to look at all of the cards in that zone and find a card with certain properties from among them. After searching the deck, the deck's owner must shuffle their deck, and they typically must reveal the card they searched for to the opponent as well.
If a player is instructed to search a hidden zone for a card with certain properties, such as color, level, or card type, that player does not need to find any cards with those properties, even if they have cards with those properties in their deck, as since the hidden zone is private they cannot prove that they have a card with those properties in that zone. In Magic: the Gathering parlance, this is called "fail to find."
If a player is instructed to search for X cards of a certain property, they must either find 0 or X cards with that property, with no in-between. For example, a player may choose to use Munkarun, Elder Sister Deity of the Holy Tomb's Life Burst to search their deck for zero or two <Angel> SIGNI with the same level, but they may not search for exactly one. In contrast, a player may choose to find only a white SIGNI or only a red SIGNI with Get Dantalian.
