Three princesses escaped from Planet Omega and loved Earth as their second home, protecting the peace. The youngest sister, Cosmo Angel Yui, an Antarctic expedition member, is troubled by an approach from a colleague. As a member of a superhuman race, her older sister has forbidden her from having physical relations with Earthlings. A serious incident occurs! A firm promise is shaken! "Is... this SEX!? It... feels too good..." [BAD END]