Aya Tatsugami

Aya Tatsugami (辰神彩, Tatsugami Aya) is a character in Durarara!! SH. She is the older sister of Himeka and Ai Tatsugami, who mysteriously disappears after investigating the Headless Rider.

Characteristics
Aya has strong beliefs in doing what is right, even turning her father in for his crimes in loaning money illicitly. However, her involvement in her father's arrest lead to her being reprimanded by her mother. Years later, she's even stabbed by a client of her father's. This causes her to not only question her place in the world, but to develop a deep hatred for the world's seeming unfairness.

After seeing the Headless Rider on television, Aya begins to form an obsession over it (Celty), convinced that it is the savior which would save them from this cruel world. However, Aya's sister consistently point out that this absurd belief is just Aya's way of running from her problems.

Background
Aya turned her father in for his illegal money dealings. However, her involvement in her father's arrest lead to her being reprimanded by her mother. Years later, she's even stabbed by a client of her father's. This causes her to not only question her place in the world, but to develop a deep hatred for the world's seeming unfairness.

Serial Kidnapping Arc
She disappears as a part of a mass serial kidnapping. It is later revealed that she, her sister Ai and the other kidnapies were actually Headless Rider fanatics who ran away to join the cult.

Trivia

 * It is revealed in an Epitome of Eighteen Histories that she was a co-worker of Kazane Kinomiya as a part-time writer.