If you're looking for manga similar to Heaven's Door, you might like these titles.
In the future, robots are more than machines. Autonomous “cyber-persons” with A.I. brains are part of society, interacting with humans and growing their own culture. In fact, they may be surpassing humans, as biological homo sapiens and their own world have begun to die out. But are humans truly disappearing, or are robots the new “humans”?
After being nicknamed "Princess Goth Chick" because of her behavior in elementary school, Komachi Tamamura spent three years as a hikikomori. Since she continued to ditch even after in high school, her sister Chacha sent her Nanado Nado Nado, a friendship android to lead Komachi back to real life interactions in school! Nanado's official name is "Code 7D-O", but she is rarely called that. She is bright and optimistic, and doesn't think too much about things. She can perform general living activities such as talking and eating, just like humans, so that she does not seem to be an android. While she can emit a beam from the eyes and has 100 language modes, she does not have enough arithmetic functions for high school.
Includes the following chapters:
Kurumi, the dumb android. Chiaki, her guardian with a few screws loose. Sakina, calm, composed, and easily amused. Shiyuki, the only sane(?) girl. Follow their exciting high school life as they tinker with and pamper Kurumi, as well as talk about nothing in particular.
PIPPI, a humanoid computer developed to predict earthquakes, estimates that a global-scale cataclysm will occur in eight years. Though the computer also announces that the accompanying danger of human extinction can be avoided by taking a series of specific steps, the process deviates so far from normality that people are thrown into a state of chaos and doubt.
In the future, androids live side by side with humans – but not as their equals, as their slaves. Though they look identical, these androids must display a holographic ring over their heads so the difference is clear. One day, a boy named Rikuo finds abnormal activity patterns in the logs of his own android, and alongside his friend Masaki, he sets forth to find where the android has been. Much to their surprise, the duo discovers a secret café known as Eve no Jikan with a single rule: within its walls, there must be no discrimination between humans and robots. In this place, androids appear to be human and are even displaying signs of independence – a trait that should not be possible. Rikou finds his perceptions increasingly challenged as he struggles to come to terms with his own android, and the relationship between man and machines...
A secret social experiment is led by two Japanese engineers, having an android every move, expression and decision decided through a majority vote from a collective of ca. 3000 randomly chosen people. The vote system offers the opportunity to any member of the collective to set forward his/her proposition. The 3 most proposed actions as well as two propositions made only once are submitted to the majority vote.Rules and systems have been set to ensure the dynamism of that community, and to prevent identification of people and places where the android evolves in modern-day Japan. And so the Dēmokratía android came to life.