 No one who came to the high tech underwater theme park LeMU on May 1st, 2017 were expecting anything out of the ordinary. None of the seven young people who found themselves deep underwater on that day had any idea what was to happen. But when a sudden accident traps them together in the quickly flooding facility, with no means of contacting the outside, what was to be an ordinary day turns into a harrowing five days where life-and-death hang in the balance. With only 119 hours until the destabilized facility collapses from the water pressure, the tide and tension inside LeMU continues to quickly rise. Unable to help themselves, unable to escape, the seven people turn to each other for comfort, support, and hope. Two young men, Takeshi Kuranari, an emotional university student, and the Kid, a teenager suffering from amnesia, are the filters through which this world is seen. As one or the other, different elements of the mysteries of LeMU, the accident, and the five heroines are revealed. Only by experiencing the story through both of them can the truth be revealed, and everyone be saved. And, as time runs out, feelings between the seven continue to grow, and glimmers of love among the desperation shines through. Will it be enough to undo the disaster? Can true feelings save the seven from tragedy? Only time, what little of it is left, will tell.