Circadia

Hiroki Katayama is your average high school kid. He moved to the undersea city Blue Genesis because of his foster dad, his uncle Shigeru's, job. Right after he got there, he could tell this place wasn't exactly normal. There were all these rumors, like ghosts showing up, or people getting attacked by monsters called Nightmares. Everyone acted like it was a joke, but still... The night they moved in, some weird creature showed up right in front of him. It called itself Navi and said if they lived together, it could awaken his psychic powers. Navi told him there's some huge disaster happening in the real world right now, and if they don't stop it, everything's going down for good. It sounded like something that had nothing to do with him, but just like the rumors said, Nightmares really were wandering around Blue Genesis. So even though he didn't want any part of this mess, he started looking for other espers just like Navi told him to. [Translated from the official website]

The game begins when Hiroki Katayama (the main character of the game) arrives an underwater city and as soon as his plane arrives at the airport he meet the spirit of a mysterious woman. After that he meets Yumi Asakura for the first time. A little later he meets his uncle and he takes him to his apartment. Since that day his life will change forever. When he arrives at his uncle apartment, at night he meet an strange creature that will be with him all the game, and tells him that the world is in danger of collapse and he must help him to save it. That creature show him the other world and a few minutes later when they return to the human world some strange creatures attacks him and the little creature provide him the power to destroy them. The next day he meets Yumi Asakura again and go with her to the high school and the adventure will start them.