Aiber is a professional con-man who "sometimes helps L do his dirty work."
Aiber is a tall man with slicked back, shoulder-length blond hair and light blue eyes. He has chiseled facial features with high cheekbones and a prominent jaw. He dresses professionally, usually in a suit and black coat.
Aiber is a professional con-man who possesses the special ability to blend in with various types of social groups. Death Note 13: How to Read states that he speaks "numerous languages and often assumes false identities." Having these abilities and his "good looks," he is able to build trust with certain individuals and extract information from them.
The book also states that he gets the biggest thrills from swindling and living "life on the edge."
Aiber plays the role of Eraldo Coil, one of L's detective aliases, during the investigation of the Yotsuba Group. Aiber uses his initial "A," just like L, when communicating through computers. Aiber dislikes guns and the idea of using them, but when the Task Force is chasing Higuchi, he fires a shot at Higuchi's head (and misses).
After L's death, Light Yagami writes Aiber's real name in his Death Note. In the manga, Aiber dies of liver cancer in a hospital in Paris, France, with his family at his bedside. In the anime, Aiber dies of alcohol poisoning or presumably of a heart attack in front of his son and wife.
According to Obata, his editor told him that Aiber was a "sarcastic, comic relief" character. Obata said that he wishes that he could have drawn Aiber to be "more comedic." Obata believes that if he drew Aiber and Wedy to look "a little bit more original," Ohba could have included the characters in a larger role in Death Note.
- The fact that his real name is Thierry and that he died in France with his family suggests that he is French. He is also seen staying near the famous landmark known as the Arc de Triomphe in Paris during his call to the Yotsuba Group. The surname Morrello is Italian, but he may be of Italian descent.
- 'Thierry' is also a corrupted spelling of the romaji for 'cherry'. His name is therefore also a pun on the morello cherry.
- Aiber hates guns and only reluctantly handles one when Higuchi flees the Sakura TV after firing at Soichiro Yagami.
- It is implied that, along with Wedy, Aiber briefly worked under L during the Los Angeles BB Serial Murder Cases.