Mysterion

Leon Schwarts is a simple sailor, enjoying his time at sea and his breaks on land, while doing his best to avoid sleeping and the nightmares that haunt him. During a trip to London, Leon's boat runs across what seems to be a deserted ship, only to find a single survivor, the beautiful girl Lapis. However, Lapis has secrets of her own that she is willing to go to extreme lengths to keep. This meeting starts a string of events that changes Leon's life forever...

(from mangaupdates)