When you first unlock the use of fairies in game, you are only allowed to keep 5 fairies at one time. However, there is a way to raise the maximum amount. Each map in Adventure Mode has a "final" stage with Ganon as the final enemy. (Killing him will trigger the credits) Each final stage completed will raise your maximum fairy count by one. There are nine full maps, so it is possible to hold up to 14 fairies if all final stages are cleared.