Kuroha's younger sisters abruptly visit Sueharu's house to tell him that she has developed amnesia. All her memories from summer break onward are gone, and they stop right when she was about to confess to Sueharu. So she suggests starting over from the moment of her own confession and erasing everything she did during the cultural festival. But Kuroha's behavior is making Shirokusa suspicious...
So they're basically like 
my own sisters, then?
إنّهنّ كأخواتي الصّغار إذًا؟
Sie sind also im Grunde auch so was
wie meine Schwestern, wie?
Es decir, que son como mis hermanitas.
Es decir, que sois como mis hermanas.
C’est comme si on était sœurs,
alors !
Quindi in pratica è come 
se fossero mie sorelle, giusto?
Ou seja, elas são como minhas irmãs, certo?
Значит, вы и мне тоже как сёстры?