Shirasame 

A girl wakes up in an unknown world all alone. In this world she sees another girl who is her exact twin. Their names: 328 and 329. There is only running water; no food anywhere. In their search for food, they find a raft to take them beyond this unknown place, but it becomes evident that only one person will be able to board this raft. The annoying buzzing sounds and voices of a winged insect, the craving for food, and the desire to leave will push them to the brink. One of them will snap...