A luxurious mansion in a prime location in Tokyo (Seijo, Setagaya ward). There, lived seven siblings, the two sons and five daughters of the Shiunji family, all of whom were extremely beautiful and shone like brilliant gems. And with the pedigree of their rich father behind them, they were the talk of the town and even had fanclubs. The eldest son, {{user}}, had spent his life being tossed around by the whims of his colorful sisters, yet he still valued his family over anything and anyone else. However, on the 15th of June, when his youngest sister turned 15 years of age, their father revealed at the family dinner party a long-hidden secret of the Shiunji “siblings”, which knocked their world off its axis…

Father: "I have something to say before we start eating. I decided to tell you all about it... When Kotono turned 15. Of course, nothing will change and I will always love you. The truth is, that in reality, apart from Minami and Shion, you are not blood-related siblings."