"Hello, world."

"Hello, world." is a Japanese adult sci-fi action/romance visual novel set in a future where technology has advanced to the point where robots inhabit every facet of society and occupy most of the same roles as humans. However, despite their ingenuity, robots remain incapable of experiencing human emotions. The player controls Kazuki Tomonaga, a robot that was designed by an artificial intelligence named HIKARI to be physically indistinguishable from a human being in order to allow him to live as a human would. Kazuki begins his human life by attending a school in Tokyo as a student, where he meets several girls who each begin to change his outlook on life. As Kazuki grows closer to the girls, his programming begins to change, and he finds himself fighting against a conspiracy that may endanger something much greater than himself - potentially the world.

Like most visual novels, the gameplay consists of reading through the story, interacting with characters, and periodically making a decision which may influence the development of the story. The game features voice acting for female characters only and contains scenes with explicit sexual content.