A typical summer night turns hotter than usual at the Obinata household when a young author named Shuu Asuou turns up and announces that he’ll be living with them from now on! Shuu explains that he has married their sister Shima and that he will be staying at the house while awaiting her return. But when she doesn’t turn up, he proclaims that he is there to stay for good! But did the hot-headed eldest Obinata sibling, Shima, really marry the timid-looking Shuu? If so, why?! And where is Shima anyway? Meanwhile, what does the oldest brother, Taiga, have to say about all this? Will the other three Obinata siblings accept Shuu? Or will they go on hunger–strike to drive Shuu out of the house? Will Shuu ever realize his dream of adopting the Obinatas and being called “Father” by the whole lot? And just who is Yuuta, and why does he look and sound like a Yakuza?