Brothers Aki and Shima are upset by the sudden appearance of a "fourth brother" in the Kaidou family, and Haru's excessively affectionate attitude towards Ren makes Aki explode with rage. Meanwhile, Haru happens to witness a car accident in the city. Since then, Haru begins leaving Ren alone in the apartment. On top of that, while Ren is home alone, one of Haru's customers from the host club forces her way into the apartment, and--?!
and it just happens to be 
the youngest's birthday.
Und der jüngste von ihnen
hat auch noch Geburtstag.
y además es el cumpleaños del menor.
y además es el cumpleaños del pequeño.
C’est aussi l’anniversaire 
du petit dernier.
è pure il compleanno del più piccolo!
Além disso, será o aniversário do caçula.