Gaiden is a Japanese-language word meaning "side story" or "tale", used to refer to an anecdote or supplementary biography of a person. However, some gaiden are retold stories in the perspective of a different character, this is Arashi's tale.

Mensa was sure life couldn't get any worse, what with getting sorted into Ravenclaw, as well as being the daughter of Bellatrix. To having an annoying cousin that seemed to love taunting her or following her around, a pair of red headed trouble makers declaring themselves her friends, and a first year Gryffindor avoiding her at every turn. Now The Dark Lord was back? Merlin.