Kochira, Haha Naru Hoshi Yori

Summary

A virus said to have come from space caused unprecedented damage to Earth. It has been a long time since that catastrophe, and now there are only six of us in Ikebukuro. The city has been reduced in size and its buildings have been torn down and decorated with green grass and blue water. The scent of an air conditioner comes from somewhere ... "This is Mother Earth!" And we are doing well today! One morning, Kanako and five other girls woke up on a cruise ship. The inside of the ship was silent, with no traces of other people. The only memory they could recall was each other's names and the fact that they were on vacation together. With nothing else to do, they began to explore the ship.