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.
acting like the mopey little sister 
character whose brother
Deine aufmüpfige Haltung als Schwester
deutet darauf hin, dass du nicht willst,
Actúas como una hermana enojada
Actúas como una hermana enfadada
mais en fait, tu es juste jalouse
Ma ti comporti proprio
come la tipica sorellina che si finge fredda
Você é praticamente como
 a irmãzinha emburrada
что ты ведёшь себя, как капризная сестра,
чьего братика увела к себе другая девушка.