Maid (メイド Meido) is Ryuunosuke's artificial intelligence (AI) program he wrote personally. Originally, Ryuunosuke designed Maid to filter and automatically reply to his cellphone messages and emails to save him time. However, Ryuunosuke keeps expanding Maid's AI ability. Maid is now capable of blocking and replying to a message or email by her own preference, using new words she has recently learned from other messages, emails, or the Internet in the reply, giving Sorata solid advice for his computer game program, anticipating people's emotions with cameras, writing computer or cellphone viruses and sending them out by herself, or even hacking into Suiko's computer to steal information. The only way to distinguish Maid's message from those from a human is that she replies too quickly. Ryuunosuke lets Maid enter a social networking service, with most people who meet her not realizing she is an AI program. According to Ryuunosuke, his ultimate goal is to give Maid an artificial body and become a real human.
As running the Maid program requires a lot of hard drive space and RAM, Ryuunosuke is forced to keep her working in the high standard server set in room 102 of the Sakura Dormitory, while giving orders and receiving the results via the Internet when he is absent from the room. On the computer, Maid is shown as a 3D model (designed by Misaki) on the bottom right corner of the screen, and will be shown using various tools and stationary depending on her current work. Maid appears to have a crush on Ryuunosuke, although it is unknown whether she has developed the feelings herself or if it is simply a part of her program design. After Rita falls in love with Ryuunosuke and kisses him, Maid starts a fight with her on the Internet since Ryuunosuke constantly lets Maid handle Rita's love letters and emails. Maid even asks Sorata to go to England and help her eliminate Rita.
Maid was originally a text-based AI program, giving her replies to contacts via text messages. This was presented when Sorata wanted to befriend Ryuunosuke when he first moved in, but got replies from Maid-chan herself.
However, Ryuunosuke kept expanding her capabilities. With help from Misaki, who developed a 3D model for the program, she was made into the program she is known today.