WARNING!: SPOILERS!

Aya is a very quiet person and never really smiles due to an incident which resulted in the murder of his parents and left his sister in a coma. Aya's real name is Ran Fujimiya , he has tooken his sister's name, 'Aya', who was put into coma by Reiji Takatori's car. Aya's main purpose is to destroy Reiji for placing his sister in a coma and to avenge the death of his parents (Reiji killed them purposely). In return for working for Weiß, Aya gets payed and uses the money for his sister's hospital bills..Hospital bills hurt you know.

Overall Aya is a really depressing person who keeps his true feelings to himself most of the time(Yes, he really does care about the other members of Weiß and his sister! )