The project began when Aniplex producer Ryo Oyama, while conceiving a new original anime, met Production I.G producer Tetsuya Nakatake, who was also developing an original anime beyond his company's usual image, leading them to launch the project together.

From the earliest planning stages, the show was intended for Fuji TV's Noitamina programming block, with the additional new concept of bringing robot anime elements into that block for the first time.

Popular illustrator redjuice was chosen for the original character designs because the creators felt his modern, fresh art style would fit the series' worldview and give the original project a necessary 'edge.'

The core concept of 'using friends as weapons/servants' was the earliest idea pitched, and series composer Hiroyuki Yoshino said it took about half a year of development before this idea evolved into the story's key concept, the 'Voids'.

Character designer redjuice drew several hairstyle options for Ayase, including short hair and hair worn down, but the moment he showed a rough sketch of her with a ponytail, the staff unanimously chose it on the spot.

Kanon Kusama was not part of the original script; she was created because redjuice, during a production meeting, spontaneously drew a 'glasses-wearing class president' character on his own, and this design was adopted directly into the series.

Tsugumi's design was reportedly the most heavily sketched character in early planning, even more than heroine Inori; her cat-ear-like head accessories were conceived by redjuice as a spontaneous idea turning 'communicator' into 'cat ears.'

The robot companion Funeru's design was created by redjuice, who has said he was consciously influenced by the 'Tachikoma' robots from Ghost in the Shell; its name comes from the English word 'funeral.'

Inori's orange stage outfit, nicknamed the 'goldfish dress,' was designed to evoke butterflies and angels; an early version had a connecting piece over the chest, but director Tetsuro Araki asked for it to be removed, resulting in the daring open design from chest to navel.

The show's opening and ending theme performers were chosen through a supercell audition held between May and July 2011 among about 2,000 candidates: 15-year-old Koeda was selected to sing the opening theme, while 17-year-old Chelly was chosen to perform as the in-universe band EGOIST's vocalist for the insert songs and ending theme.

Haruka Ouma's character, Shu's stepmother, was designed with a deliberately casual personality who strips off her clothes upon entering the house and wanders around in underwear, remaining unfazed even when encountering Inori living in the house.

The character Hare Menjo's name uses an unusual reading (written with the kanji for 'festival' but read as 'Hare'), an idea from sub-series composer Ichiro Okouchi, which other staff members joked was not normally readable.

Sub-series composer Ichiro Okouchi joined the project partly as a favor, since he had previously served as series composer on Code Geass while Yoshino was sub-composer, and they had an understanding that when Yoshino became series composer on a future project, Okouchi would return the favor as sub-composer.