Mayuka, who crash-landed at Yoshizumi Hisashi’s house, is still living. She is in the mode of Hisashi’s younger sister with a secret weapon, a raygun. Mayuka revives her ultimate weapon, Akiho, on Earth and prepares to take on the battle on her mother planet, but her feelings also sprout in her Akiho. With Fuyuno appearing further, she is full of younger sisters around Hisashi! Mayuka really likes Hisashi among the many girls who think of her brother.