High schooler Sugatami Akira has had an unrequited love for classmate Kitajima Miyoko since they were in grade school together, but Akira has always been too nervous to confess to Miyoko. At the same time, off in space and racing towards the Earth is an alien being that has been travelling alone for a long time. The being spots the Earth and decides to land in order to find out if she can fulfill her mission of spreading her race across the Galaxy.

On his way home from school Akira is accidently knocked to the ground. When he gets home he finds that he has somehow gotten a chain with a small ball with six spikes on it around his neck. As Akira tries to remove the chain the ball suddenly grows to a flying sphere about almost two meters in diameter. The big sphere now has two big eyes and a huge grin full of teeth, and it starts to speak to Akira. The ball is a space princess named Demelta C Bete Brumanto, and she wants to mate with Akira so that she can produce more of her kind. Akira doesn't think this makes sense because they are so different, but Demelta states that there is no problem. Akira gets mad at Demelta and grabs one of her spikes, at which point she transforms into a beautiful, busty, naked, and nordic-looking girl. Demelta is not pleased with this transformation but she isn't deterred from using her new appearance to try to get Akira to mate with her. However, Akira finds the idea wrong, particularly since he wants Miyoko to be his "first." But Akira and Demelta are chained together with an unbreakable chain that won't come off of Akira until Demelta gets pregnant.