Basara and his father, Jin, wait for the Basara's new step sisters who has yet to meet, but they are late. After Basara goes to the bathroom to change, he encounters a girl who has red hair, and it turns out that she is his younger step-sister, Mio. Mio and her sister Maria introduce themselves to Bassara. The next day, Basara wakes up with a feeling of discomfort, and finds Mio on his belly, she tells him that it is the her service. Basara lives with his two sisters, getting along with them well, and takes a family photograph. When Mio goes shopping, she is attacked, but Basara appears and helps her. On a hill overlooking the sunset, Mio tells Basara that thanks to him she was saved. Jin goes away from home on business, and Mio suddenly asks Basara to leave the house, and it becomes clear that Mio is actually a demon. Maria tries to repel Bassara using magic, but it fails. Basara, who turns out to be a "Hero", asks the two to please leave the house, and then he calls Jin and asks for an explanation over the telephone. Afterwards, Mio and the Maria are attacked on a hill by an enemy, but Bassara rushes over immediately and goes to help Mio.
