the mother is correct and the biggest issue of the "ISEKAI" theme:
How dare they impose their own values while they kidnapped other people and ask them to solve their problem.
i dont understand,
while i know that the MC (Arata) and other girls are not blood-related (just got the info from his parents, for whatever reason they keep the truth)
they still his sisters right?
who basically growing up together from children/more than a decade? does it change anything ...