Amai Ao

Amai Ao (天井 亜雄) is a minor antagonist in the Toaru Majutsu no Index series. Originally a researcher of the First Production Plan of the Sisters Project to develop military clones of Misaka Mikoto, he was later brought back into the project after it was reused for the Level 6 Shift experiment.

Appearance
Amai Ao has a skinny build and a gaunt look which is amplified by his long, wavy and greasy-looking black hair. He is always seen wearing his lab coat even after the experiments ended.

Background
He was a researcher and the superintendent during the First Production Plan of the Sisters Project and specialized in creating personality data with self-learning capabilities, however, he was soon relieved of his duties after it was discovered there was a flaw in the plan, as such he spirals into debt. Ao was later called back after the project was reused for the Level 6 Shift experiment, and was tasked to direct the experiments. During the experiments, Ao invested heavily the project, hoping for a return after it concluded.

He later associates himself with outside organizations such as the Science Association that are opposed to Academy City to repay his debts.

Sisters Arc
After Touma defeats Accelerator and ends the experiment, Ao becomes heavily indebted due to investing in the project and plans, as well a deliberate attempt by the City to push all liability on him. As a result, he plans to move to a rival organization outside of Academy City. He later implants a virus into Last Order a few days after the end of the project, which would order the clones under the command of Last Order to attack people. Despite this, he did not anticipate for her to escape her incubation chamber, which puts his plan into jeopardy. He later tells the research institute that he is taking a vacation while he searches for Last Order, who eludes him for a week.

Three Stories Arc
He is later seen by Accelerator outside of a certain restaurant (a different one in each adaptation) entering his car. Realizing who his watcher is, Ao immediately speeds off. However he later returns to the restaurant to retrieve Last Order, who is already weakened by leaving her incubation tank too early and having the virus ready to activate. Ao takes her to the now abandoned Sisters Project Research Facility,  as he has nowhere to go since traffic in and out of Academy City has been limited since someone has breached the city's security.

When Accelerator arrives to retrieve Last Order Ao tries to run him over but Accelerator's power negates the attempt and destroys his car while keeping Last Order safe. Scared, Ao tries to run away but gets stuck by his car's door. Using his vector powers, Accelerator hits Ao with his door making him lose consciousness. Ao later regains consciousness at the same time Accelerator is finishing up his using of his vector powers to delete the virus programmed into Last Order. Ao successfully shoots Accelerator in the head as the latter is using all his vector calculations on Last Order and could not deflect the bullet. He later tries to shoot Last Order as well after Accelerator successfully deleted the virus in her system but she is saved by Accelerator, who survived the gunshot and deflects the bullet back towards Ao, injuring his hand.

Accelerator tries to attack Ao, though fails as he loses consciousness due to the gunshot. Seeing Accelerator fall, Ao tries to shoot Accelerator again but is shot by Yoshikawa Kikyou in the back who just arrived. Ao is visibly surprised by Kikyou's intervention, as he states that her personality of weighing risks and opportunities should've prevented her from doing this. Kikyou tells him that she is aware of that and states that she really did not want to be a researcher but instead a teacher and berates Ao for attacking children, causing both to pull their guns on each other. Ao comments that what she is displaying is not kindness but strength, at which point both fire simultaneously. Ao dies but Kikyou is saved by Heaven Canceler, who explains that Accelerator used his vector powers to prevent any blood spilling from her arteries that were ruptured by Ao's gunshot.

Magic God Othinus Arc
In the final recreation of the world by Othinus created specifically to break Touma's spirit, known as the Version_Omega world in-text, where several characters from the original world have been "saved" or have not experienced great tragedy, both Kikyou and Ao have a friendly relationship with each other as well as with Accelerator.

Later, after Touma's spirit has been finally broken and is trying to decide on how he should have himself killed, Last Order, several of the Sisters, and Misaka Worst are in the festival in the Academy City accompanied by Accelerator, Yoshikawa Kikyou, and Amai Ao. Accelerator complains on being in the festival, to which Kikyou states that there is nothing wrong with getting a little excited, as someone who saved every last one of the 20,000 plus Sisters deserves at least that much for him. Amai Ao however, comments on how it costs a lot. He points to Accelerator on how the clones are staring restlessly on food stands, while Misaka Worst is egging them on.

Sisters Arc
He objects to the manager of the project's security for distributing the experiment to various facilities. Ao worries about the interests of the project being split-up, but is calmed by the manager after he explains to him that those who will receive gains from the experiment are the one who are still running it at the time of the project's completion. He leaves his office shortly thereafter.

After the failure of the Level 6 Shift Project, Ao becomes heavily indebted due to investing in the project and plans, as well a deliberate attempt by the City to push all liability on him. As a result, he plans to move to a rival organization outside of Academy City.

Design evolution
Despite being 30 years old, Amai Ao is described by Haimura as a young researcher like Kihara Amata. His sketches for Ao have been lost digitally but can still be seen in his art book, rainbow spectrum: colors.