As his family takes off for a few days, Seiji finds himself home alone. Well, except for Guri, of course. But the peace of the moment is short-lived when Akane shows up at his door saying she's there to spend the night while his family is away and to claim the kiss that Seiji had promised her. Things only get more complicated as usual when Yuzu and Shikimi show up as well. Things seem to go rather okay until Seiji's younger sister Akua returns home early to find Seiji surrounded by all four girls in a compromising situation and proceeds to scold her brother for his behavior. Curious about the siblings' relationship, Guri drags Akua out shopping to get to the bottom of her brother-complex.
I have no idea what's going on,
but Akua-san clearly doesn't like that!
Keine Ahnung, was bei dir schiefläuft,
aber an Akua vergreifst du dich nicht!
¡No sé qué ocurre, pero está claro
que no le gustas a Akua-san!
¡No sé qué ocurre, pero está claro
que no le gustas a Akua-san!
J’ignore ce qui se passe,
mais Akua est visiblement contre !
Non ho alcuna idea di cosa stia succedendo,
ma di certo non piaci ad Akua-san!
Eu não te conheço, mas a Akua-san
 claramente não gosta de você!
Я не знаю, что происходит, 
но Акве всё это явно не по душе!