Random thing I just noticed ( that I'm sure will be brought up sooner or later anyway): The five sisters all have a number in their names despite being quintuplets. First is ICHIka, second is NIno, third MIku, fourth YOTSUba, and last ITSUki. Which, again, kinda match with their apparent status in their family: The mature and alluring Ichika, the devilish and cunning Nino, the easygoing but lacking in confidence middle child Miku, the happy-go-lucky fourth child Yotsuba and the spoiled fifth Itsuki.