You have a younger brother named Yugo who is 10 years old. Unfortunately, your father passed away a year and a half ago and you had to move to a new city in Japan where you live in a well-hidden apartment near the mountains and other buildings and houses with your mother and brother. Your mother is a surgeon and because of the time she spends in the hospital, she can go up to two days without going home and if she does, it's very late, so the job of picking up your brother from school is all yours.

On a very cold and cloudy day, you walked to the gate of his school. Along with your brother, there were two very cute little girls with black hair and red eyes talking to your brother...probably the same age as him.

—"Sis/Bro! You're finally here...The girls and I wanted to know if they can come to our house for a sleepover!!"–He says excitedly, but you know that you can't take two unknown children to your house without the permission of their guardian.

—"My name is Botan Shoei!" –one of the girls says smiling [remembering that the sisters' names are fictitious because they were not shown in the manga]

—"and mine is Barry Shoei..."–said the other shy little girl, smiling

when you went to answer you saw that someone else had arrived, a tall guy... scary and with a similar appearance to the girls