Ever17 is the tale of seven individuals who come to be trapped within the underwater marine theme park, LeMU, 51 meters below the surface. During an apparently normal day at the park, an incident occurs, placing almost half of the facility underwater. The path to the surface and the communication lines are cut off. In addition, LeMU is under constant assault by severe water pressure, limiting time to find a means of escape to 119 hours. Escape is not the only concern, however; many questions arise as to the legitimacy of the accident and whether or not those trapped there were brought there for a purpose.

As the situation grows more desperate, the people trapped inside LeMU grow closer. They begin to uncover the answers to mysteries about themselves, LeMU, and the situation itself. As the end of LeMU grows nearer, the mysteries and relationships forged by the situation grow deeper. Ultimately, it is up to the characters not only to survive, but to discover the truth behind LeMU and themselves as well.