The importance of fuku in this text, or the bad luck that Yunior writes about in the opening of the text, is shown through the way that it is explained as some impersonal force that is much bigger and stronger than any of the characters and which cannot be resisted. Fuku becomes the explanation for any bad luck and is normally linked to some kind of curse or ill will stretching back into the past. However, as the opening section makes clear, there is something that a character can do to try and prevent the fuku from ruining their lives completely:
...there was only one way to prevent disaster from coiling around you, only one surefire counterspell that would keep you and your family safe. Not surprisingly, it was a word. A simple word (followed usually by a vigorous crossing of index fingers).
This word, "zafa," is used by Yunior when he explores his own motives for writing the story and setting down to paper what happened to Oscar. He says that this book is a "zafa of sorts," and goes on to describe it as his "own counterspell." Yunior thus hopes to maintain his identity and protect himself from fuku through telling the story of Oscar, his friend who suffered (according to Junior) because of fuku.