Submerged

The game is set in a dystopian future when global warming has flooded the world. Miku and her younger brother Taku drift into a city partially submerged beneath ocean water with only the tallest buildings protruding from the sea. The two have fled home from their father following his descent into alcoholism since the unfortunate death of their mother; his violent actions towards them have resulted in Taku becoming seriously injured. Taking refuge in the top of a clock tower, Miku begins to explore the city in her motorized fishing boat in search of supplies to treat Taku. She scales buildings, locating relief crates that had been parachuted in during the crisis. The whole time she is observed by aquatic beings who are revealed to be survivors of the city that have undergone a complete mutation to better thrive in their new environment. Miku also realizes to her shock that she herself is now mutating in a similar way. Eventually she locates the final crate and Taku recovers. They are then confronted by the mutants who perform some ritual that purges Miku of her mutation, making her human again. The siblings then take their leave and move on from the city.