Trouble! Sister Room

Urara is an ordinary student, living alone. He lives a boring life, and wants to get a girlfriend. He has two childhood friends, Maria and Arisa. Maria is older than him, but she is beautiful, smart and kind-hearted. Arisa is her younger sister. One night, he has a dream of an octopus staring at him, and says, "You've been singled out. You must choose someone to save the earth." When he wakes up, there are Maria and Arisa sitting in front of him in strange clothes. But they don't know why they come to his place. At that moment, a voice comes from above, and tells them that Urara has been singled out as a representative of humans, and Maria and Arisa have been chosen by Urara. His mission is to choose a partner, or everything will be destroyed.... Their strange cohabitation starts now....