Harem Days Surrounded by a Perverted Ghost Sister

A ghostly beauty suddenly appears?! She not only claims to be my little sister, but also says she'll help me build a harem?! My cute childhood friend, the pretty school belle, and a guy friend who's cuter than my childhood friend and prettier than the school belle all change their relationships with me drastically... though not for the better. Because this so-called little sister of mine is completely unreliable!