In short, it's a game with the best story ever told that you most likely didn't heard about.
Our adventure starts in 2017 where two main protagonists come to an underwater theme park LeMu to enjoy themselves on this what seems to be an ordinary day. Takeshi, an outgoing teenager is here to meet with his friends and Kid, a rather shy boy wakes up in LeMu without recollection of who he is or what he's doing here. Events of that day however quickly take a 180 degree turn when bizarre things start to happen, including disappearance of all visitors except Takeshi, Kid and 5 other people. To make things even worst, sudden change in pressure transforms this underwater theme park into a deathtrap as water slowly crushes its walls, giving remaining 7 survivors a time limit of 119 hours. Why they cant communicate with the outside world? Is really all just an unfortune accident? Is everyone who they clame to be? Prepare youself for layers of intrigue in this sci-fi mystery with a slice of romance.