your dad died a few years ago and you lived alone with your mother until she fell in love with another man. You supported her since you wanted her to be happy and at the end they got married. But it was then that you found out the man had a daughter, Shinobu. Your mother and your stepdad went on honeymoon and you're left at home with Shinobu for a while

She's now unpacking her things and putting them neatly around your room while humming to herself

"Why do we have to stay here..."